explanation blue bibcodes open ADS page with paths to full text
Author name code: greve
ADS astronomy entries on 2022-09-14
author:"Greve, Albert"
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Title: The EMIR multi-band mm-wave receiver for the IRAM 30-m
telescope
Authors: Carter, M.; Lazareff, B.; Maier, D.; Chenu, J. -Y.; Fontana,
A. -L.; Bortolotti, Y.; Boucher, C.; Navarrini, A.; Blanchet, S.;
Greve, A.; John, D.; Kramer, C.; Morel, F.; Navarro, S.; Peñalver,
J.; Schuster, K. F.; Thum, C.
2012A&A...538A..89C Altcode:
<BR /> Aims: The prime motivation of this project was to design and
build a state-of-art mm-wave heterodyne receiver system to enhance
the observing throughput of the IRAM 30-m radiotelescope. More
specifically, the requirements were i) state-of-art noise performance
for spectroscopic observations; ii) simultaneous dual polarization
and dual-frequency observing; iii) coverage of the atmospheric
transmission windows from 83 to 360 GHz; iv) compact footprint and
minimal maintenance. <BR /> Methods: Key elements for low noise
performance of heterodyne mixers are the superconducting Niobium
junctions, operating at ≃4 K. These junctions are embedded in
carefully designed coupling structures; furthermore, since atmospheric
radiation is a significant contributor to the system noise budget,
all mixers are either sideband separating or sideband rejecting. To
achieve low noise, it is also essential to maximize the coupling of the
receiver to the astronomical source, and to minimize the coupling to
thermal radiation from the ground-based environment; this is achieved
through mirror optics that realize a wavelength-independent coupling
to the telescope. A flexible configuration of mirrors and frequency
selective surfaces permits various combinations of frequency bands,
as well as dual-load radiometric calibration. Low noise intermediate
frequency amplifiers and bias electronics also play an important role in
the system performance. <BR /> Results: The EMIR receiver in operation
at the 30 m telescope offers four frequency bands: B1: 83-117 GHz,
B2: 129-174 GHz, B3: 200-267 GHz, and B4: 260-360 GHz. In each band,
the two orthogonal polarizations are observed simultaneously. Dual-band
combinations B1/2 B1/3, and B2/4 are available. Bands 1 and 4 (also 3 as
of Nov.-2011) feature sideband separation. In dual-band configuration,
including sideband separation and polarization diplexing, up to eight
IF channels are delivered to the spectrometers, totaling up to 64 GHz
of signal bandwidth (of which 32 GHz can be transported and processed
by spectrometers, status Nov.-2011). The EMIR receiver has been in
continuous operation for more than two years and has allowed, through
a qualitative jump in performance, observations not possible before,
as shown by a few selected examples of astronomical results. <P />This
article is dedicated to the memory of our colleague Matt who initiated
and played a key role in this project.
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Title: A dynamic thermal model for design and control of an
800-element open-air radio telescope
Authors: Bremer, Michael; Greve, Albert
2011SPIE.8336E..0UB Altcode: 2011SPIE.8336E..29B
In earlier work we have described the thermal modelling for design and
control of a fully insulated, and sometimes ventilated, high precision
radio telescope. For such an insulated telescope the modelling of the
time-variable dynamic influence of the thermal environment (air, sky
and ground radiation, insolation) is relatively simple. The modelling
becomes however quite complex for an open-air radio telescope where
each individual member of the reflector backup structure (BUS) and
the support structure (fork or yoke) is exposed under a different
and time-dependent aspect angle to the thermal environment, which
applies in particular to solar radiation. We present a time-dependent
800-element thermal model of an open-air telescope. Using the IRAM
30-m radio telescope as the basic mechanical structure, we explain
how the temperature induced, real-time pointing and reflector surface
deformations can be derived when using as input the day of the year,
the thermal environment, and the geographic position of the telescope
and its changing pointing direction. Thermal modelling and results
similar to those reported here can be used for radio telescope design
and real-time control of pointing and surface adjustment of a telescope
with active panels.
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Title: The apparent "reversed" motion of gas and stars in M 82
Authors: Greve, A.
2011A&A...529A..51G Altcode:
We summarize earlier and unpublished long-slit spectroscopic
measurements of radial velocities of ionized gas and stars along
and parallel to M 82's major axis to a radial distance of ~±2.5 kpc
(~±140”) from the center. In the position-velocity diagram, these
measurements indicate a velocity reversal of ~100 km s<SUP>-1</SUP>
of gas and/or stars at ~±1.0 kpc (~±50-70”) on either side of
the center, outside the bar. Although seen in earlier observations,
and perhaps neglected because they were assumed to be only an effect
of heavy local extinction, the positional symmetry of the velocity
reversal with respect to the center of M 82, as well as the absence
of the reversal in the motion of stars seen in the near-IR Ca ii
absorption lines, points to another origin. M 82's two-armed spiral,
as outlined by Mayya et al. (2005, ApJ, 628, L33), may explain a
part of the velocity reversal, although this interpretation leaves
inconsistencies so that other explanations must also be investigated. A
simple, conclusive explanation of the velocity reversal has not yet been
found. While restricted observationally in radial distance to ~120”
(2 kpc), the near-IR stellar Ca ii absorption lines, which do not show
the velocity reversal, indicate a flat radial velocity curve of the
stellar disk that remained after the encounter with M 81.
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Title: Extinction A<SUB>V</SUB>, R towards emission nebulae derived
from common upper level Paschen-Balmer hydrogen lines
Authors: Greve, A.
2010A&A...518A..62G Altcode:
The reddening in and around emission nebulae is characterized by the
extinction A<SUB>V</SUB> and the ratio R of the absolute-to-selective
absorption. Both are usually derived from the photometry of a single
star or cluster stars that are associated with an emission nebula. Using
the parameterized reddening relation published by Cardelli et al. (1989,
ApJ, 345, 245), we show that A<SUB>V</SUB> and R can be derived with
good precision from the observation of a set of common upper level
Paschen-Balmer hydrogen line ratios. The use of common upper level line
ratios has the advantage of being nearly independent of the excitation
condition of the nebula (n<SUB>e</SUB>, T<SUB>e</SUB>). The line ratio
method can be applied in regions where no stars are available for
photometry. <P />Partially based on observations made at ESO, La Silla.
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Title: The Beam Pattern of Reflector Antennas With Buckled Panels
Authors: Greve, A.; Morris, D.; Penalver, J.; Thum, C.; Bremer, M.
2010ITAP...58..959G Altcode:
On high precision reflector telescopes the transient thermal panel
buckling can have an effective rms-value comparable to the errors
in the adjustment of the reflector panels. Under this condition,
high signal-to-noise radio holography of high spatial resolution
can reveal the characteristic signature of panel buckling in the
beam pattern and can map the surface deformation of the buckling,
while lower signal-to-noise Moon limb scans may see the buckling
only under favorable conditions. Detailed diffraction calculations,
and some observations, indicate (1) that the panel buckling produces
diffraction rings and/or diffraction spokes, (2) that panel buckling
in azimuthal direction may have a smaller degrading effect than panel
buckling in radial direction because for azimuthal buckling the energy
is spread more uniformly over a large solid angle, and (3) that the
coverage of the reflector aperture with buckled panels determines the
multiplicity of the diffraction rings and/or diffraction spokes.
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Title: Thermal Design and Thermal Behaviour of Radio Telescopes and
their Enclosures
Authors: Greve, Albert; Bremer, Michael
2010ASSL..364.....G Altcode:
No abstract at ADS
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Title: Performance Improvement of a Flexible Telescope Through
Metrology and Active Control
Authors: Greve, Albert; Karcher, Hans Jurgen
2009IEEEP..97.1412G Altcode:
A radio telescope is a flexible structure under the influence of
gravity, temperature, and wind. Even after all passive means of
telescope construction have been applied, the residual structural
deformations of a high precision telescope may still lead to focus,
pointing, and path-length errors and a loss in gain that exceed
the performance specifications. Gravity-induced deformations can be
calculated and corrected with high precision. While the time-variable
nature of temperature- and wind-induced deformations can only partially
be explored in numerical simulations, their control requires the input
from metrology. Corrections can be made through the telescope control
system but also, to some extent, through deformable mirror surfaces. The
progress in metrology and the correction of certain telescope errors
are described.
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Title: The brightness temperature of Mercury at mm-wavelengths
Authors: Greve, A.; Thum, C.; Moreno, R.; Yan, N.
2009A&A...495..639G Altcode:
We present observations of Mercury made with the IRAM 30-m telescope
at 3, 2 and 1.3 mm wavelength (90, 150 and 230 GHz) during the years
1985-2005; we derive from these data the disk-averaged brightness
temperatures. The observations at 3 mm combined with those by Epstein
& Andrew allow a separation of the data into 40° wide longitude
intervals and by this an investigation of the disk-averaged brightness
temperature with Mercury's longitude. From the new mm-wavelength data,
and data taken from the literature, we derive the disk-averaged
brightness temperature as a function of wavelength. On Mercury's
night side a significant decrease in brightness temperature occurs
towards shorter wavelengths. We use the three surface models (A,B,C)
discussed by Mitchell & de Pater and calculate for the cool
and hot surface region the corrresponding diurnal variation of the
disk-averaged brightness temperature at 90 GHz. For the same models we
calculate the variation of the disk-averaged brightness temperature
with wavelength between 1.3 mm and 37 mm, on Mercury's midnight side
and noon side. Although the scatter in the observations is large,
there seems to be a marginally better agreement with model B and A.
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Title: A Global 86 GHz VLBI Survey of Compact Radio Sources
Authors: Lee, Sang-Sung; Lobanov, Andrei P.; Krichbaum, Thomas P.;
Witzel, Arno; Zensus, Anton; Bremer, Michael; Greve, Albert; Grewing,
Michael
2008AJ....136..159L Altcode: 2008arXiv0803.4035L
We present results from a large 86 GHz global very long baseline
interferometry (VLBI) survey of compact radio sources. The main goal of
the survey is to increase by factors of 3-5 the total number of objects
accessible for future 3 mm VLBI imaging. The survey observations reach
a baseline sensitivity of 0.1 Jy and an image sensitivity of better
than 10 mJy beam<SUP>-1</SUP>. A total of 127 compact radio sources
have been observed. The observations have yielded images for 109
sources, extending the database of the sources imaged at 86 GHz with
VLBI observation by a factor of 5, and only six sources have not been
detected. The remaining 12 objects have been detected but could not be
imaged due to insufficient closure phase information. Radio galaxies are
less compact than quasars and BL Lac objects on the sub-milliarcsecond
scale. The flux densities and sizes of the core and jet components
of all imaged sources have been estimated using Gaussian model
fitting. From these measurements, brightness temperatures have been
calculated, taking into account the resolution limits of the data. The
cores of 70% of the imaged sources are resolved. The core brightness
temperatures of the sources peak at ~10<SUP>11</SUP> K and only 1%
have brightness temperatures higher than 10<SUP>12</SUP> K. The cores
of intraday variable (IDV) sources are smaller in angular size than
those of non-IDV sources, and so yield higher brightness temperatures.
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Title: Mechanical Measurements of the ALMA Prototype Antennas
Authors: Greve, Albert; Mangum, Jeff
2008IAPM...50b..66G Altcode: 2007arXiv0710.5629G
The specifications of the Atacama Large Millimeter Array (ALMA)
have placed stringent requirements on the mechanical performance of
its antennas. As part of the evaluation process of the VertexRSI and
Alcatel EIE Consortium (AEC) ALMA prototype antennas, measurements
of the path length, thermal, and azimuth bearing performance were
made under a variety of weather conditions and observing modes. The
results of mechanical measurements, reported here, are compared to
the antenna specifications.
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Title: Long-term observations of Uranus and Neptune at 90 GHz with
the IRAM 30 m telescope. (1985-2005)
Authors: Kramer, C.; Moreno, R.; Greve, A.
2008A&A...482..359K Altcode: 2008arXiv0801.4452K
Context: The planets Uranus and Neptune with small apparent diameters
are primary calibration standards. <BR />Aims: We investigate their
variability at ~90 GHz using archived data taken with the IRAM 30 m
telescope during the 20 year period 1985 to 2005. <BR />Methods: We
calibrate the planetary observations against non-variable secondary
standards (NGC 7027, NGC 7538, W3OH, K3-50A) observed almost
simultaneously. <BR />Results: Between 1985 and 2005, the viewing
angle of Uranus changed from south-pole to equatorial. We find that
the disk brightness temperature declines by almost 10% (~2σ) over
this time span indicating that the south-pole region is significantly
brighter than average. Our finding is consistent with recent long-term
radio observations at 8.6 GHz. Both data sets show a rapid decrease of
the Uranus brightness temperature during 1993, indicating a temporal,
planetary scale change. We do not find indications for a variation of
Neptune's brightness temperature at the 8% level. <BR />Conclusions:
If Uranus is to be used as a calibration source, and if accuracies
better than 10% are required, the Uranus sub-earth point latitude
needs to be taken into account.
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Title: Towards the Event Horizon: High Resolution VLBI Imaging of
Nuclei of Active Galaxies
Authors: Krichbaum, T. P.; Graham, D. A.; Witzel, A.; Zensus, J. A.;
Greve, A.; Grewing, M.; Bremer, M.; Doeleman, S.; Phillips, R. B.;
Rogers, A. E. E.; Fagg, H.; Strittmatter, P.; Ziurys, L.
2007ecf..book..189K Altcode: 2006astro.ph..7077K
Very Long Baseline Interferometry at millimetre wavelengths (mm-VLBI)
allows to image compact galactic and extragalactic radio sources with
microarcsecond resolution, unreachable by other astronomical observing
techniques. Future global VLBI at millimetre wavelengths therefore
should allow to map,with a spatial resolution of only a few to a few
ten gravitational radii, the direct vicinity of the Super Massive
Black Holes (SMBH) located in the centres of nearby galaxies. With
the reduced intrinsic self-absorption at short wavelengths, mm- VLBI
opens a direct view onto the often jet-producing "central engine".
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Title: Characteristics and Performance of the North American ALMA
Prototype Antenna
Authors: Mangum, J. G.; Baars, J. W. M.; Greve, A.; Lucas, R.; Snel,
R.; Wallace, P.
2006ASPC..356..253M Altcode:
The submillimeter antennas of the Atacama Large Millimeter Array
(ALMA) have specifications that are beyond the current state of
the art in accurate reflector antenna technology. Considering that
as many as 64 of these antennas will eventually be needed, the ALMA
partners AUI/NRAO and ESO each agreed to acquire a prototype antenna,
and subject these to an extensive evaluation program. In this paper we
summarize the performance of the ALMA North American prototype antenna.
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Title: NGC 2146's starburst region and extended structure
Authors: Greve, A.; Neininger, N.; Sievers, A.; Tarchi, A.
2006A&A...459..441G Altcode:
We present mm-wavelength and optical observations of the starburst
region in NGC 2146. This region of ~4 kpc diameter contains a
well-ordered distribution of stars, gas, and dust, and a well-ordered
rotation. The possible anomalies found in our observation are a warped
CO distribution and an increase in the CO line width at the NW edge
of the starburst region. The investigation of a possible encounter or
merger origin of the starburst may therefore have to concentrate on the
distorted outer structure of the galaxy. There are three large-scale
features of ~20 kpc extent, two of which give the impression of being
stellar sub-systems. The third feature is an incomplete and expanding
ring of H ii regions and stars, apparently indicating an event that
occurred some 300 Myr ago.
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Title: Evaluation of the ALMA Prototype Antennas
Authors: Mangum, Jeffrey G.; Baars, Jacob W. M.; Greve, Albert; Lucas,
Robert; Snel, Ralph C.; Wallace, Patrick; Holdaway, Mark
2006PASP..118.1257M Altcode: 2006PASP..118.1260M; 2006astro.ph..9329M
The ALMA (Atacama Large Millimeter Array) North American and European
prototype antennas have been evaluated by a variety of measurement
systems to quantify the major performance specifications. Near-field
holography was used to set the reflector surfaces to 17 μm
rms. Pointing and fast-switching performance was determined with an
optical telescope and by millimeter-wavelength radiometry, yielding 2"
absolute and 0.6" offset pointing accuracies. Path-length stability
was measured to be <~20 μm over 10 minute time periods using
optical measurement devices. Dynamical performance was studied with a
set of accelerometers, providing data on wind-induced tracking errors
and structural deformation. Considering all measurements made during
this evaluation, both prototype antennas meet the major ALMA antenna
performance specifications. <P />The performance results presented
in this publication were part of a comprehensive technical evaluation
process used to evaluate the ALMA prototype antennas, which concluded
in 2005 April.
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Title: Calculated thermal behavior of ventilated high precision
radio telescopes
Authors: Greve, A.; Bremer, M.
2006IAPM...48....9G Altcode: 2006IAPM...48....9.
Radio telescopes that operate at millimeter and sub-millimeter
wavelengths need a reflector-surface precision of a few tens of
microns and a pointing accuracy of a few arcseconds. When built
in a conventional way from steel and aluminum, as in the case of
larger-diameter telescopes, thermal control must be applied to reduce
temperature-induced deformations, in particular of the reflector backup
structure. We illustrate that it is possible to make model calculations
- for instance, during the design phase - that simulate the thermal
behavior and the operation of a telescope when servo-loop-controlled
ventilation or climatization (air-conditioned ventilation) of the backup
structure is applied. We explain the technique of model calculations,
and present as an example the calculated thermal behavior of a
ventilated 64-m-diameter telescope and of the climatized 30-m IRAM
telescope. It is explained that the thermal control of a telescope
mount is less demanding if frequent pointing corrections can be made.
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Title: APEX: the Atacama Pathfinder EXperiment
Authors: Güsten, R.; Booth, R. S.; Cesarsky, C.; Menten, K. M.;
Agurto, C.; Anciaux, M.; Azagra, F.; Belitsky, V.; Belloche, A.;
Bergman, P.; De Breuck, C.; Comito, C.; Dumke, M.; Duran, C.; Esch,
W.; Fluxa, J.; Greve, A.; Hafok, H.; Häupl, W.; Helldner, L.;
Henseler, A.; Heyminck, S.; Johansson, L. E.; Kasemann, C.; Klein,
B.; Korn, A.; Kreysa, E.; Kurz, R.; Lapkin, I.; Leurini, S.; Lis, D.;
Lundgren, A.; Mac-Auliffe, F.; Martinez, M.; Melnick, J.; Morris,
D.; Muders, D.; Nyman, L. A.; Olberg, M.; Olivares, R.; Pantaleev,
M.; Patel, N.; Pausch, K.; Philipp, S. D.; Philipps, S.; Sridharan,
T. K.; Polehampton, E.; Reveret, V.; Risacher, C.; Roa, M.; Sauer, P.;
Schilke, P.; Santana, J.; Schneider, G.; Sepulveda, J.; Siringo, G.;
Spyromilio, J.; Stenvers, K. -H.; van der Tak, F.; Torres, D.; Vanzi,
L.; Vassilev, V.; Weiss, A.; Willmeroth, K.; Wunsch, A.; Wyrowski, F.
2006SPIE.6267E..14G Altcode:
APEX, the Atacama Pathfinder Experiment, has been successfully
commissioned and is in operation now. This novel submillimeter telescope
is located at 5107 m altitude on Llano de Chajnantor in the Chilean High
Andes, on what is considered one of the world's outstanding sites for
submillimeter astronomy. The primary reflector with 12 m diameter has
been carefully adjusted by means of holography. Its surface smoothness
of 17-18 μm makes APEX suitable for observations up to 200 μm,
through all atmospheric submm windows accessible from the ground.
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Title: A multi-layered thermal model of backup structures for
mm-wavelength radio telescopes
Authors: Greve, A.; Smith, D. R.; Bremer, M.
2006SPIE.6271E..0KG Altcode: 2006SPIE.6271E..20G
An unfavourable influence that degrades the performance of any
millimeter wavelength radio telescope is the deformation of the
reflector surface due to temperature differences in the supporting
backup structure. To avoid, or at least reduce this influence, the
backup structures are typically protected by a rear side cladding,
insulation at the panel inner side, and ventilation or climatization
of the air inside the backup structure. During the design of a
mm-wavelength telescope, the layout of a thermal protection system is
made, based on experience gained on other telescopes, and on thermal
model calculations of the complete backup structure. The available
thermal programs allow today the construction of a multi-layered
backup structure model, consisting of the backup structure tube
network, without and with ventilation/climatization, the panels,
insulation behind the panels, and the rear side cladding. We provide a
guideline for the construction of such a multi-layered thermal model,
and demonstrate that realistic temperature gradients across and through
a backup structure can be calculated. These gradients can be used in a
finite element model to calculate the reflector surface deformations,
which can be used in a diffraction program to calculate the radio
beam pattern.
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Title: A global 86 GHz VLBI survey of compact radio sources
Authors: Lee, Sang-Sung; Lobanov, A. P.; Krichbaum, T. P.; Witzel,
A.; Zensus, A.; Bremer, M.; Greve, A.; Grewing, M.
2006evn..confE...4L Altcode: 2006PoS....36E...4L
We present results from a large global VLBI survey of compact radio
sources at 86 GHz begun in October 2001. The main goal of the survey
was to increase the total number of objects accessible for future
3-mm VLBI imaging by factors of 3 ~ 5. The survey data attained the
baseline sensitivity of 0.1 Jy, and image sensitivity of better than
10 mJy/beam. To date, a total of 127 compact radio sources have been
observed. The observations have yielded images for 109 sources, and
only 6 sources have not been detected. Flux densities and sizes of
core and jet components of all detected sources have been measured
using Gaussian model fitting. From these measurements, brightness
temperatures have been estimated, taking into account resolution
limits of the data. Here, we compare the brightness temperatures of
the cores and secondary jet components with similar estimates obtained
from surveys at longer wavelengths (e.g. 15 GHz). This approach can
be used to study the phenomena related to mechanisms of initial jet
acceleration (accelerating or decelerating sub-pc jets?) and jet
composition (electron-positron or electron-proton plasma?).
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Title: Extending VLBI to 2mm and 1mm Wavelengths
Authors: Doeleman, S. S.; Phillips, R. B.; Rogers, A. E. E.; Attridge,
J. M.; Titus, M. A.; Smythe, D. L.; Cappallo, R. J.; Buretta, T. A.;
Whitney, A. R.; Krichbaum, T.; Graham, D. A.; Alef, W.; Polatidis,
A.; Bach, U.; Kraus, A.; Witzel, A.; Wilson, T.; Zensus, J. A.; Greve,
A.; Grewing, M.; Freund, R.; Ziurys, L.; Fagg, H.; Strittmatter, P.
2005ASPC..340..605D Altcode:
Technical VLBI experiments have been carried out at wavelengths shorter
than 3mm, yielding the highest angular resolutions ever attained in any
waveband. Long baseline detections of AGN at 129GHz, 147GHz, and 230GHz
have fringe spacings (λ/D) of 56, 49, and 34μas respectively. We
also present the first 129GHz VLBI map of the SiO masers associated
with the evolved star VY CMa.
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Title: Improvement of the IRAM 30-m Telescope From Temperature
Measurements and Finite-Element Calculations
Authors: Greve, A.; Bremer, M.; Penalver, J.; Raffin, P.; Morris, D.
2005ITAP...53..851G Altcode:
Millimeter wavelength radio telescopes built in a conventional way from
steel and aluminum require elaborate thermal control to guarantee small
structural deformations and good observational performance. We describe
the temperature monitoring system of the Institut de Radioastronomie
Millimetrique 30-m telescope and the use of temperature measurements
in finite-element calculations of structural deformations. These
calculations reproduce with good precision the measured thermal
deformations of the telescope and allow the investigation and
localization of thermally important elements in the telescope
structure. The data are used for calculation of temperature induced
main reflector surface deformations and of the associated actual beam
pattern, and for prediction and real-time correction of the focus. The
pointing cannot be fully predicted since the available finite-element
model does not include the Nasmyth focus cabin (and the concrete
pedestal). The long-term investigation of the telescope's thermal
behavior led to an improvement of the thermal control system and to
a better performance of the telescope.
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Title: Neutral Hydrogen Absorption at the Center of NGC 2146
Authors: Tarchi, A.; Greve, A.; Peck, A.; Neininger, N.; Wills, K.;
Pedlar, A.; Klein, U.
2004ASPC..320..112T Altcode:
No abstract at ADS
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Title: A 230 GHz heterodyne receiver array for the IRAM 30 m telescope
Authors: Schuster, K. -F.; Boucher, C.; Brunswig, W.; Carter, M.;
Chenu, J. -Y.; Foullieux, B.; Greve, A.; John, D.; Lazareff, B.;
Navarro, S.; Perrigouard, A.; Pollet, J. -L.; Sievers, A.; Thum, C.;
Wiesemeyer, H.
2004A&A...423.1171S Altcode:
We describe the technical concept, properties, and performance of HERA
(HEterodyne Receiver Array) at the IRAM 30 m telescope. HERA is a
multibeam, waveguide SIS receiver that greatly improves mapping speed
in various observing modes and also provides possibilities for new
high-sensitivity observing of small sources. Future extensions with a
second polarization module will permit spectro-polarimetry. We present
some examples of astronomical maps with HERA.
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Title: Neutral hydrogen absorption at the centre of NGC 2146
Authors: Tarchi, A.; Greve, A.; Peck, A. B.; Neininger, N.; Wills,
K. A.; Pedlar, A.; Klein, U.
2004MNRAS.351..339T Altcode: 2003astro.ph..9447T
We present 1.4-GHz HI absorption line observations towards the
starburst in NGC 2146, made with the Very Large Array and the
Multi-Element Radio-Linked Interferometer Network. The HI gas has
a rotating disc/ring structure with column densities between 6 and
18 × 10<SUP>21</SUP> atom cm<SUP>-2</SUP>. The HI absorption has a
uniform spatial and velocity distribution, and does not reveal any
anomalous material concentration or velocity in the central region of
the galaxy which might indicate an encounter with another galaxy or a
far-evolved merger. We conclude that the signs of an encounter causing
the starburst should be searched for in the outer regions of the galaxy.
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Title: HI absorption at the center of NGC2146
Authors: Tarchi, A.; Greve, A.; Peck, A. B.; Neininger, N.; Wills,
K. A.; Pedlar, A.; Klein, U.
2004astro.ph..3127T Altcode:
We present 1.4 GHz HI absorption line observations towards the starburst
in NGC2146, made with the VLA and MERLIN. The HI gas has a rotating
disk/ring structure with column densities between 6 and 18 x 10(21)
atoms cm(-2). The HI absorption has a uniform spatial and velocity
distribution, and does not reveal any anomalous material concentration
or velocity in the central region of the galaxy which might indicate
an encounter with another galaxy or a far-evolved merger. We conclude
that the signs of an encounter causing the starburst should be searched
for in the outer regions of the galaxy.
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Title: The rotating visible outflow in M 82
Authors: Greve, A.
2004A&A...416...67G Altcode:
M 82's minor axis outflow is seen at visible wavelengths as more or
less regular hollow cones on both sides of the galactic disk. The
outflowing material is expected to entrain the rotation, or part of
the rotation, of the disk where the outflow originates. From the
conservation of angular momentum it is furthermore expected that
the outflowing material continues to rotate at large distances from
the disk, although probably with smaller velocity because of radial
divergence of the cones. We provide evidence of this kinematic picture
from long-slit spectra of the cone wall H<SUB>\alpha</SUB>, [NII]
and [SII] emission lines taken at ±20” (±300 pc) and ∼±40”
(∼±600 pc) distance from the center and parallel to the minor axis,
from data extracted from the literature, and from a cone model fit
of the data. The angular momentum which is entrained in the outflow
and eventually dissipated is a small fraction of the total angular
momentum associated with the stars and gas in the central part of the
disk. We compare our observation of the visible outflow with the outflow
of dragged-out material investigated in mm-wavelength CO by other
observers. It seems that the material observed at visible wavelengths
is confined to narrow cones, and blows out at velocities larger than
the escape velocity of the galaxy. The dragged-out material moves at
slower velocities and on wider cones, and may fall back into the galaxy.
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Title: Towards the Event Horizon - The Vicinity of AGN at
Micro-Arcsecond Resolution
Authors: Krichbaum, T. P.; Graham, D. A.; Alef, W.; Kraus, A.; Sohn,
B. W.; Bach, U.; Polatidis, A.; Witzel, A.; Zensus, J. A.; Bremer,
M.; Greve, A.; Grewing, M.; Doeleman, S.; Phillips, R. B.; Rogers,
A. E. E.; Fagg, H.; Strittmatter, P.; Ziurys, L.; Conway, J.; Booth,
R. S.; Urpo, S.
2004evn..conf...15K Altcode: 2004astro.ph.11487K
We summarize the present status of VLBI experiments at 3 mm (86 GHz),
2 mm (129-150 GHz) and 1.3 mm (215-230 GHz). We present and discuss
a new 3 mm VLBI map of M 87, which has a spatial resolution of only
∼ 20 Schwarzschild radii. We discuss recent results for Sgr A*
and argue in favor of new observations within an extended European
mm-VLBI network, in order to search for variability. We discuss the
possibilities to image the `event horizon' of a super-massive black
hole at wavelengths < 2 mm, and conclude that the addition of
large and sensitive millimetre telescopes such as CARMA, the SMA,
the LMT and ALMA will be crucial for this. (astro-ph/0411487)
---------------------------------------------------------
Title: Millimetre-VLBI Monitoring of AGN with Sub-milliarcsecond
Resolution
Authors: Pagels, A.; Krichbaum, T. P.; Graham, D. A.; Alef, W.;
Kadler, M.; Kraus, A.; Klare, A.; Witzel, J. A.; Zensus, A.; Greve,
A.; Grewing, M.; Booth, R.; Conway, J.
2004evn..conf....7P Altcode: 2004astro.ph..9328P
Global millimetre VLBI allows detailed studies of the most central jet
regions of AGN with unprecedent spatial resolution of a few 100--1000
Schwartzschild radii to be made. Study of these regions will help to
answer the question how the highly relativistic AGN jets are launched
and collimated. Since the early 1990s, bright mm-sources have been
observed with global 3 mm VLBI. Here we present new images from
an ongoing systematic analysis of the available observations. In
particular, we focus on the structure and structural evolution
of the best observed AGN jets, taking 3C 454.3 as a characteristic
example. This core-dominated and highly variable quasar shows a complex
morphology with individual jet components accelerating superluminally
towards the outer structure. We briefly discuss the X-ray properties
of 3C 454.3 and present its radio- to X-ray large-scale brightness
distribution. (astro-ph/0409328)
---------------------------------------------------------
Title: Millimeter VLBI and Variability in AGN Jets
Authors: Krichbaum, T. P.; Graham, D. A.; Witzel, A.; Zensus, J. A.;
Greve, A.; Ungerechts, H.; Grewing, M.
2003ASPC..299..249K Altcode: 2003astro.ph..8043K; 2003heba.conf..249K
Millimeter-VLBI images probe as deep as never before the nuclei
of AGN. VLBI at 147 GHz yields transatlantic fringes for the first
time. Now we can begin to study the relation between jet kinematics
and spectral activity with a few ten micro-arcsecond resolution.
---------------------------------------------------------
Title: 2mm Wavelength VLBI: SiO Masers in the Envelope of VYCMa
Authors: Doeleman, S. S.; Phillips, R. B.; Rogers, A. E. E.; Attridge,
J. M.; Titus, M. A.; Smythe, D. L.; Cappallo, R. J.; Buretta, T. A.;
Whitney, A. R.; Krichbaum, T.; Graham, D. A.; Alef, W.; Polatidis,
A.; Bach, U.; Witzel, A.; Zensus, J. A.; Greve, A.; Grewing, M.;
Freund, R.; Strittmatter, P.; Ziurys, L.; Wilson, T.; Fagg, H.
2002AAS...20111508D Altcode: 2002BAAS...34R1291D
In April 2002 an array of antennas operating at 129GHz successfully
detected VLBI fringes on both continuum AGN and SiO spectral line
sources. The 129GHz fringes on maser sources represent the highest
frequency spectral line VLBI detections to date. The AGN 3C279 was
detected on long baselines at both 129GHz (and at 147GHz) yielding
fringe spacings of 50-56 micro arc seconds, an angular resolution
record. The array consisted of the Kitt Peak 12m antenna and the
Heinrich Hertz 10m Telescope (HHT), both operatedby the Arizona Radio
Observatory, and the IRAM 30m dish on Pico Veleta (Spain). At 129GHz,
a number of evolved stars and several young stellar objects exhibit
strong SiO maser emission in the v=1 J=3-2 transition. We present
maps of the v=1 J=3-2 maser emission towards the hypergiant VYCMa and
discuss the relation of the maser features to the optical asymmetric
nebula surrounding the star. Future high frequency VLBI using these
telescopes will include continuum observations of the radio source at
the Galactic Center, SgrA*, and higher frequency maser lines including
HCN and methanol.
---------------------------------------------------------
Title: 147 GHz VLBI observations: Detection of 3C 273 and 3C 279 on
the 3100 km baseline Metsähovi - Pico Veleta
Authors: Greve, A.; Könönen, P.; Graham, D. A.; Wiik, K.; Krichbaum,
T. P.; Conway, J.; Rantakyrö, F.; Urpo, S.; Grewing, M.; Booth,
R. S.; Zensus, J. A.; John, D.; Navarro, S.; Mujunen, A.; Ritakari,
J.; Peltonen, J.; Sjöman, P.; Oinaskallio, E.; Berton, M.
2002A&A...390L..19G Altcode:
We report a successful VLBI observation at 147 GHz (2.1 mm) on the 3
100 km long baseline between the telescopes at Metsähovi (Finland)
and Pico Veleta (Spain). The sources 3C 273B and 3C 279 were detected
with a SNR of ~ 10. For these sources we estimate that 25-30% of the
total flux is detectable as correlated flux on the 3 100 km baseline,
which gives at 147 GHz a lower limit of the brightness temperature of
the inner VLBI jet region of ~ 1x10<SUP>10</SUP> K.
---------------------------------------------------------
Title: 1st Global mm-VLBI at 512 Mbits
Authors: Graham, D. A.; Alef, W.; Krichbaum, T. P.; Kraus, A.; Greve,
A.; Conway, J. E.; Attridge, J. M.; Buretta, T. A.; Shute, P. A.;
Titus, M. A.
2002evn..conf...67G Altcode:
At the end of the 86 GHz CMVA session in October 2001, a first mm-VLBI
observation was conducted which used a recording bit-rate of 512 Mbits/s
utilizing the Mk IV recording system. The four radio telescopes involved
were Onsala, Effelsberg, Pico Veleta, and Haystack. In 20 hours of
observing time 8 sources --- 1156+295, 1633+382, 1803+784, 3C273,
3C274, 3C345, 3C454.3, BL Lac --- were observed in a snapshot-like
mode. All sources could be detected thanks to the 40% sensitivity
increase obtained by doubling the usual recording rate, and simple
maps could be made.
---------------------------------------------------------
Title: 2mm Wavelength VLBI of SiO Masers and AGN
Authors: Doeleman, S. S.; Phillips, R. B.; Rogers, A. E. E.; Attridge,
J. M.; Titus, M.; Smythe, D.; Cappallo, R.; Buretta, T.; Whitney,
A. R.; Krichbaum, T. P.; Graham, D. A.; Alef, W.; Polatidis, A. G.;
Bach, U.; Witzel, A.; Zensus, J. A.; Greve, A.; Grewing, M.; Freund,
R.; Strittmatter, P.; Ziurys, L.; Wilson, T. L.; Fagg, H.; Gay, G.
2002evn..conf..223D Altcode: 2002astro.ph..7072D
In April 2002 an array of antennas operating at 129GHz successfully
detected VLBI fringes on both continuum AGN and SiO spectral line
sources. The 129GHz fringes represent the highest frequency spectral
line VLBI detections to date. The array consisted of the University of
Arizona Kitt Peak 12m antenna, the Sub Millimeter Telescope Observatory
10m (HHT), and the IRAM 30m dish on Pico Veleta. These observations
are the first fringes at any frequency at the SMTO and we discuss the
technical challenges involved. <P />At 129GHz, a number of evolved stars
and several young stellar objects exhibit strong SiO maser emission in
the v = 1 J = 3-2 transition. Preliminary cross power spectra of VYCMa
on the HHT-Kitt Peak baseline (∼190km) are consistent with multiple
spatially separate maser spots associated with the star. We discuss
phase mapping this emission and the implications for constraining the
SiO maser pumping mechanisms and circumstellar dynamics around these
objects. Future observations will include continuum observations of
the radio source at the Galactic Center, SgrA*, and higher frequency
maser lines including HCN and methanol.
---------------------------------------------------------
Title: VLBI observations at 147 GHz: first detection of transatlantic
fringes in bright AGN
Authors: Krichbaum, T. P.; Graham, D. A.; Alef, W.; Polatidis, A. G.;
Bach, U.; Witzel, A.; Zensus, J. A.; Greve, A.; Grewing, M.; Doeleman,
S. S.; Phillips, R. M.; Rogers, A. E. E.; Titus, M. A.; Fagg, H.;
Strittmatter, P.; Wilson, T. L.; Ziurys, L.; Freund, R.; Peltonen,
P. K. J.; Urpo, S.; Rantakyr, F.; Conway, J. E.; Booth, R. S.
2002evn..conf..125K Altcode: 2002astro.ph..7022K
At 147 GHz (2 mm wavelength), we detected three prominent AGN (NRAO
150, 3C 279, 1633+382) with Very Long Baseline Interferometry (VLBI)
with an angular resolution of only ∼18 micro-arcseconds. This is a
new world record in radio interferometry and astronomical imaging and
opens fascinating future possibilities to directly image and study
the innermost regions in quasars and other active galactic nuclei.
---------------------------------------------------------
Title: A search for radio supernovae and supernova remnants in the
region of NGC 1569's super star clusters
Authors: Greve, A.; Tarchi, A.; Hüttemeister, S.; de Grijs, R.;
van der Hulst, J. M.; Garrington, S. T.; Neininger, N.
2002A&A...381..825G Altcode: 2001astro.ph.11221G
We have used MERLIN, at 1.4 and 5 GHz, to search for radio supernovae
(RSNe) and supernova remnants (SNRs) in the unobscured irregular dwarf
galaxy NGC 1569, and in particular in the region of its super star
clusters (SSCs) A and B. Throughout NGC 1569 we find some 5 RSNe and
SNRs but the SSCs and their immediate surroundings are largely devoid
of non-thermal radio sources. Even though many massive stars in the
SSCs are expected to have exploded already, when compared with M 82
and its many SSCs the absence of RSNe and SNRs in and near A and B
may seem plausible on statistical arguments. The absence of RSNe and
SNRs in and near A and B may, however, also be due to a violent and
turbulent outflow of stellar winds and supernova ejected material,
which does not provide a quiescent environment for the development of
SNRs within and near the SSCs.
---------------------------------------------------------
Title: M 82's stellar bar
Authors: Greve, A.; Wills, K. A.; Neininger, N.; Pedlar, A.
2002A&A...383...56G Altcode:
The fueling of the starburst in M 82 may be related to a stellar
bar which pushes gas towards the center where it forms stars. The
observation by McKeith et al. (1993) of the near-IR Ca II photospheric
absorption line allows a direct velocity measurement of the stars in M
82, and provides by this a confirmation of the predicted x<SUB>1</SUB>
and x<SUB>2</SUB>-orbits of the bar in M 82. From this and other
observations we find that the mass of the x<SUB>2</SUB>-orbit stars
is ~ 15% of the mass of the bar, and that the mass of the bar of 2x
10<SUP>9</SUP> M<SUB>sun</SUB> is 20-40% of M 82's mass. This mass
concentration of ~ 1 kpc extent at the center of M 82 underlines the
dynamic importance of the bar.
---------------------------------------------------------
Title: A Second Epoch of 86 GHz CMVA Polarimetry Observations of
the Quasars 3C273 and 3C279
Authors: Attridge, J. M.; Wardle, J. F. C.; Homan, D. C.; Krichbaum,
T. P.; Greve, A.
2001AAS...199.9808A Altcode: 2001BAAS...33.1454A
Observations of 3C 273 and 3C 279 taken in April 2000 with the
Coordinated Millimeter VLBI Array (CMVA) resulted in the first 86
GHz VLBI total intensity (Stokes I) and linear polarization images
of any source (Attridge 2001). As Faraday effects are proportional
to λ <SUP>2</SUP>, 86 GHz data should be less affected by Faraday
rotation and depolarization than lower frequency data. The four
antenna (FD, LA, PT, KP-12m) data defy the expectation that increased
levels of linear polarization will be found in the cores of quasars
at high frequencies, for both 3C 273 and 3C 279 display low levels
of polarization in their cores at 86 GHz. In fact, 3C 273 displays
no measurable linear polarization within a limit of 1%. The lack of
significant linear polarization in the cores of 3C 273 and 3C 279, as
well as the high rotation measures (>1000 rad m<SUP>-2</SUP>) derived
for the cores of many quasars (including 3C 273 and 3C 279) by Taylor
(1998, 2000) suggest the presence of parsec-sized Faraday screens with
organized magnetic fields near the quasar cores. If 3C 273's core is
depolarized by Faraday effects alone, the dispersion of the rotation
measure is ≳ 90000 rad m<SUP>-2</SUP> in the core. Alternately,
depolarization can be explained in the case where 89% of the magnetic
energy is contained in a tangled magnetic field. A second epoch of
86 GHz CMVA polarization observations is presented. Data were taken
in April 2001, almost exactly one year after the previous epoch, and
with twice as many antennas. In addition to confirming the previous
results, the superior resolution provided by the additional antennas
allows further restriction of the sizes of the Faraday screens in the
cores of 3C 273 and 3C 279. CMVA research at Haystack Observatory is
sponsored by the National Science Foundation.
---------------------------------------------------------
Title: Thermal model calculations of enclosures for millimeter
wavelength radio telescopes
Authors: Greve, A.; MacLeod, G.
2001RaSc...36.1111G Altcode:
Millimeter wavelength radio telescopes require a high surface
and pointing precision, which in steerable open-air telescopes is
obtained by a stiff or homologous construction and elaborate thermal
control. The perturbing thermal loads and wind loads can also be reduced
by protecting the telescope by a radome or astrodome, as applied
on several operating telescopes. However, for the new generation
telescopes of 30-m to 50-m diameter the radome or astrodome is very
large and costly, and it is a priori not certain to which extent the
internal thermal climate must be controlled, for instance, by forced
air-conditioned ventilation, to obtain a telescope of good radio
performance. We present data from the Onsala and Haystack radomes
to illustrate agreement between measurements and thermal model
calculations, and we use similar calculations to investigate the
thermal behavior of a very large astrodome and radome. The accuracy
of the calculations is sufficient for design and operational purposes.
---------------------------------------------------------
Title: HI Absorption in NGC 2146 Observed with MERLIN
Authors: Tarchi, A.; Neininger, N.; Klein, U.; Pedlar, A.; Greve, A.
2001ASPC..230..507T Altcode: 2001gddg.conf..507T
No abstract at ADS
---------------------------------------------------------
Title: Radio interferometric observations of NGC 2146
Authors: Tarchi, A.; Neininger, N.; Greve, A.; Klein, U.; Garrington,
S. T.; Muxlow, T. W. B.; Pedlar, A.; Glendenning, B. E
2001IAUS..205..180T Altcode:
We present a high-resolution 5-GHz radio continuum map of the starburst
galaxy NGC 2146 made with MERLIN and the VLA (A-array). Our observations
detect 18 compact sources, and resolves 7 of them. Additional 1.6-GHz
MERLIN observations disclose 9 sources coincident in position with
those detected at 5 GHz, which allows us to derive their spectral
indices. Only 3 sources have indices consistent with synchrotron
emission from supernova remnants or radio supernovae, while the
others have very steep inverted spectra. We suggest that the sources
with positive spectral index are optically thick ultra-compact and/or
ultra-dense H II regions with high electron densities and high emission
measures (EM > 10<SUP>7</SUP> cm<SUP>-6</SUP> pc). When compared with
M 82, the galaxy NGC 2146 lacks however a large number of supernova
remnants. We suggest that NGC 2146 is experiencing a burst of star
formation stronger than that in M 82, but being in a younger phase. In
this phase, only few stars have already exploded, whereas the others
cause strong thermal emission from compact, optically thick ionized
gas regions, around the young super starclusters. An alternative
scenario with strong free-free absorption at 1.6 GHz from foreground
ionized gas with very high emission measures (EM > 10<SUP>8</SUP>
cm<SUP>-6</SUP> pc) is discussed.
---------------------------------------------------------
Title: Compact Radio Sources in NGC 2146
Authors: Tarchi, A.; Neininger, N.; Klein, U.; Greve, A.; Garrington,
S. T.; Muxlow, T. W. B.; Pedlar, A.; Glendenning, B. E.
2001ASPC..230..509T Altcode: 2001gddg.conf..509T
No abstract at ADS
---------------------------------------------------------
Title: A high-frequency and multi-epoch VLBI study of 3C 273
Authors: Krichbaum, T. P.; Graham, D. A.; Witzel, A.; Zensus, J. A.;
Greve, A.; Grewing, M.; Marscher, A.; Beasley, A. J.
2001ASPC..250..184K Altcode: 2001astro.ph..3443K; 2001pfrg.conf..184K
We show results from a 7 year VLBI monitoring programme of 3C273 at
millimeter wavelengths. We find evidence for component acceleration,
motion or rotation of fluid dynamical patterns in the VLBI jet, and
evidence for an outburst-ejection relation between Gamma-ray flares
and the appearance of new jet components.
---------------------------------------------------------
Title: Properties of the ISM in and around NGC2146 (Oral Contribution)
Authors: Neininger, N.; Tarchi, A.; Greve, A.
2001dge..conf..157N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The minor axis outflow of NGC 2146
Authors: Greve, A.; Neininger, N.; Tarchi, A.; Sievers, A.
2000A&A...364..409G Altcode: 2000astro.ph.10116G
X-ray and optical observations have shown that the supernova explosions
and stellar winds of the starburst in NGC 2146 produce an outflow of hot
material along the minor axis. This outflow is expected to have a more
or less conical shape, on either side of the galactic plane, and cone
walls of cooler material where the outflow is in shock contact with
halo gas. We attempt to determine the geometry (diameter at the base
and opening angle) and the physical parameters (velocity and density)
of the material in the cone walls from the optical emission line and
radio observations presented here, and from published X-ray, radio,
and optical observations. We compare the outflow of NGC 2146 with the
outflow of M 82.
---------------------------------------------------------
Title: 86 GHz VLBI survey of compact radio sources
Authors: Lobanov, A. P.; Krichbaum, T. P.; Graham, D. A.; Witzel,
A.; Kraus, A.; Zensus, J. A.; Britzen, S.; Greve, A.; Grewing, M.
2000A&A...364..391L Altcode:
We present results from 86 GHz VLBI observations of 28 compact radio
sources made in April 1993. All but two of the observed objects are
active galactic nuclei. The remaining two objects are the galactic
center Sgr A<SUP>*</SUP> and the X-ray binary star Cygnus X-3. Of
the observed sources, 26 have yielded fringe detections. We present
correlated flux densities, estimate the maximum observed brightness
temperatures, and provide single Gaussian component model fits. Out
of the 17 sources with good uv-coverages, 3 are without detectable
structural details (0642+449, 0716+714, and Cygnus A), 3 have little
closure phase information (4C67.05, 1823+568, and 1928+738), and the
remaining 11 have been imaged. We study the brightness temperatures,
T_b, of the observed sources, and apply a basic population model with a
single value of the intrinsic brightness temperature, T_0, in order to
reproduce the observed distribution of T_b. Our data are consistent with
a population of sources that have T<SUB>0</SUB><= 5x 10<SUP>10</SUP>
K in the jets, and T<SUB>0</SUB> ~ 1-4x 10<SUP>11</SUP> K in the VLBI
cores. The observed T_b are also correlated with the apparent speeds
measured in the jets. For comparison, we apply the same population
scenario to a larger sample of 132 AGN observed with VLBI at 15 GHz,
and show that the distribution of brightness temperatures from that
sample is consistent with the intrinsic brightness temperature of
T<SUB>0</SUB> = 5.3x 10<SUP>11</SUP> K. The observed decrease of T_b
along the jets can be reproduced by adiabatic losses in relativistic
shocks embedded in the
---------------------------------------------------------
Title: VizieR Online Data Catalog: 86GHz VLBI survey of compact
radio sources (Lobanov+ 2000)
Authors: Lobanov, A. P.; Krichbaum, T. P.; Graham, D. A.; Witzel,
A.; Kraus, A.; Zensus, J. A.; Britzen, S.; Greve, A.; Grewing, M.
2000yCat..33640391L Altcode:
File table1 contains the list of observed sources, providing the
source coordinates (J2000) and redshift, detection status, type,
optical magnitude, and brightness temperature of the radio emission. <P
/>File table4 contains the description of the VLBI data, and provide the
observed total and correlated flux densities, the parameters of single
gaussian component model fits, and the parameters of hybrid images
of the observed sources. <P />File table5 contains multicomponent
model fits for the sources with detected extended structures and
the brightness temperatures derived from these model fits. <P />(3
data files).
---------------------------------------------------------
Title: Radio supernovae, supernova remnants and H II regions in NGC
2146 observed with MERLIN and the VLA
Authors: Tarchi, A.; Neininger, N.; Greve, A.; Klein, U.; Garrington,
S. T.; Muxlow, T. W. B.; Pedlar, A.; Glendenning, B. E.
2000A&A...358...95T Altcode: 2000astro.ph..4083T
We present a high-resolution 5-GHz radio continuum map of the starburst
galaxy NGC 2146 made with MERLIN and the VLA (A-array), in a search
of radio supernovae and supernova remnants expected to be already
produced by the most massive stars in the starburst. At 5 GHz, about
20 point sources were detected earlier by Glendenning & Kronberg
(1986) in the central 800 pc of NGC 2146. Our observations with higher
sensitivity and resolution made with MERLIN and the VLA confirm the
detection of 18 sources, and resolve 7 of them. Additional 1.6-GHz
MERLIN observations disclose 9 sources coincident in position
with those detected at 5 GHz, which allows us to derive their
spectral indices α <SUB>1.6</SUB><SUP>5</SUP>, (S<SUB>ν </SUB> ~
ν <SUP>alpha </SUP>). Only 3 sources have indices (alpha < 0)
consistent with synchrotron emission from supernova remnants or radio
supernovae, while the others have very steep inverted spectra (alpha
> 0). We suggest that the sources with positive spectral index are
optically thick ultra-compact and/or ultra-dense H II regions with high
electron densities and high emission measures (EM > 10<SUP>7</SUP>
cm<SUP>-6</SUP> pc). Minimum energy requirements indicate that these
regions may contain up to 1000 equivalent stars of type O6, comparable
to the number of stars found in super starclusters. When compared with
M 82, the galaxy NGC 2146 lacks however a large number of supernova
remnants. We suggest that NGC 2146 is experiencing a burst of star
formation stronger than that in M 82, but being in a younger phase. In
this phase, only few stars have already exploded, whereas the others
cause strong thermal emission from compact, optically thick ionized
gas regions, around the young super starclusters. We may, however, not
exclude an alternative scenario in which strong free-free absorption
at 1.6 GHz in foreground ionized gas with very high emission measures
(EM > 10<SUP>8</SUP> cm<SUP>-6</SUP> pc) hides a certain number
of supernova remnants, thus rendering for some sources the observed
inverted spectra.
---------------------------------------------------------
Title: Giant Molecular Clouds in the Dwarf Galaxy NGC 1569
Authors: Taylor, Chris L.; Hüttemeister, Susanne; Klein, Ulrich;
Greve, Albert
2000ASPC..215...51T Altcode: 2000cegf.conf...51T
No abstract at ADS
---------------------------------------------------------
Title: Polarization Calibration and Imaging with the CMVA
Authors: Attridge, J. M.; Greve, A.; Krichbaum, T. P.
1999AAS...195.1704A Altcode: 1999BAAS...31.1398A
VLBI polarization observations provide information about the structure,
orientation, and evolution of the magnetic field in synchrotron emitting
sources such as AGN. VLBI observations at centimeter wavelengths
have shown that polarized relativistic shocks in radio jets appear
as superluminal knots. In addition, magnetic field structures in
the jets of BL Lacertae objects and quasars are quite different
(e.g. Wardle et al. 1994, Ap.J., 437, 122; Cawthorne et al. 1993,
Ap.J., 416, 519). Millimeter VLBI observations have the advantage of
being relatively unaffected by Faraday rotation and opacity (Wardle et
al. 1996, in the proceedings from the Millimeter-VLBI Science Workshop
held at MIT). The high angular resolution provided by millimeter VLBI
observations will allow new outbursts which feed the radio jets to be
observed near to their point of origin. CMVA data of the quasars 3C273
and 3C279 taken in April 1997 by Krichbaum, et al. are being used to
develop and test a data calibration path for dual-polarization data
which mimics the one presented for centimeter wavelengths in NRAO's AIPS
software package. Here we present the current status of the calibration
efforts, as well as preliminary results on 3C273 and/or 3C279. CMVA
research at Haystack is sponsored by the National Science Foundation.
---------------------------------------------------------
Title: Giant molecular clouds in the dwarf galaxy NGC 1569
Authors: Taylor, C. L.; Hüttemeister, S.; Klein, U.; Greve, A.
1999A&A...349..424T Altcode: 1999astro.ph..6427T
We present CO 1->0 and 2->1 observations of the dwarf starburst
galaxy NGC 1569 with the IRAM interferometer on Plateau de Bure. We
find the CO emission is not spatially associated with the two super
star clusters in the galaxy, but rather is found in the vicinity of
an HII region. With the resolution of our data, we can resolve the CO
emission into five distinct giant molecular clouds, four are detected
at both transitions. In the 1->0 transition the sizes and linewidths
are similar to those of GMCs in the Milky Way Galaxy and other nearby
systems, with diameters ranging from ~ 40 to 50 pc and linewidths
from 4 to 9 km s(-1) . The (2-1)/(1-0) line ratios range from 0.64 +/-
0.30 to 1.31 +/- 0.60 in the different clouds. The lower line ratios
are similar to those seen in typical Galactic GMCs, while values higher
than unity are often seen in interacting or starburst galaxies. We use
the virial theorem to derive the CO-H_2 conversion factor for three
of the clouds, and we adopt an average value of 6.6 +/- 1.5 times the
Galactic conversion factor for NGC 1569 in general. We discuss the
role of the molecular gas in NGC 1569, and its relationship to the
hot component of the ISM. Finally, we compare our observations with
blue compact dwarf galaxies which have been mapped in CO.
---------------------------------------------------------
Title: Stars, H II regions, and shocked gas in the bar of NGC 1530
Authors: Greve, A.; Reynaud, D.; Downes, D.
1999A&A...348..394G Altcode:
We analyse long slit spectra taken along and perpendicular to the bar
of the galaxy NGC 1530. Our data show that the H ii regions, around
young massive stars that form in the shock-compressed gas, share the
same kinematics as the molecular gas in the x_2 orbits at the center of
the galaxy. Along the bar, the H ii regions are in the post-shock zone,
downstream of the dust lanes that contain molecular gas. Outside of the
H ii regions in the bar is faint, diffuse, ionized gas with a low Hα /
[NII] and Hα / [SII] line ratio, which confirms the presence of shocks
in the bar and supports a shock origin of the dust lanes. The measured
spatial variation of the Hα and [NII] line intensity is consistent
with the distribution of molecular gas along the dust lanes and its
high concentration near the first inner Lindblad resonance. From an
I-B image, we derive the surface brightness along the bar which we
interpret as the stellar distribution. We use these data to estimate
the mass in the various structural components of the bar. The mass of
the stars and gas in the bar is 4x 10(10) M_sun, or 12% of the total
mass of the galaxy.
---------------------------------------------------------
Title: Proposed identification of Hubble Deep Field submillimeter
source HDF 850.1
Authors: Downes, D.; Neri, R.; Greve, A.; Guilloteau, S.; Casoli,
F.; Hughes, D.; Lutz, D.; Menten, K. M.; Wilner, D. J.; Andreani,
P.; Bertoldi, F.; Carilli, C. L.; Dunlop, J.; Genzel, R.; Gueth,
F.; Ivison, R. J.; Mann, R. G.; Mellier, Y.; Oliver, S.; Peacock,
J.; Rigopoulou, D.; Rowan-Robinson, M.; Schilke, P.; Serjeant, S.;
Tacconi, L. J.; Wright, M.
1999A&A...347..809D Altcode: 1999astro.ph..7139D
The IRAM Interferometer has been used to detect the submillimeter
source HDF 850.1 found by Hughes et al. (1998) in the Hubble Deep
Field. The flux density measured at 1.3 mm (236 GHz) is 2.2+/- 0.3
(1sigma ) mJy, in agreement with the flux density measured at the
JCMT. The flux densities and upper limits measured at 3.4, 2.8,
1.3, 0.85, and 0.45 mm show that the emission comes from dust. We
suggest that the 1.3 mm dust source is associated with the optical
arc-like feature, 3-593.0, that has a photometric redshift z~ 1.7. If
the HDF 850.1 is at this redshift and unlensed, its spectral energy
distribution, combined with that of 3-593.0, matches closely that of
the ultraluminous galaxy VII Zw 31. Another possibility is that the
dust source may be gravitationally lensed by the elliptical galaxy
3-586.0 at z~ 1. The position of the dust source agrees within the
errors with that of the tentative VLA radio source 3651+1226.
---------------------------------------------------------
Title: Millimeter-VLBI science workshop
Authors: Greve, A.; Krichbaum, T. P.
1999mvlb.conf.....G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: 2nd millimeter-VLBI science workshop
Authors: Greve, A.; Krichbaum, T. P.
1999smvs.work.....G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Status of Polarization Observations with CMVA
Authors: Attridge, J. M.; Greve, A.; Krichbaum, T. P.
1999smvs.work...13A Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The beam pattern of the IRAM 30-m telescope. (a reflector
with several surface error distributions)
Authors: Greve, A.; Kramer, C.; Wild, W.
1998A&AS..133..271G Altcode:
Total power scans across the Moon around New Moon (mostly day time)
and Full Moon (night time) at 3.4 mm (88 GHz), 2.0 mm (150 GHz), 1.3
mm (230 GHz), and 0.86 mm (350 GHz) wavelength are used to derive the
beam pattern of the IRAM 30-m telescope to a level of approximately
-30 dB (0.1%) and, dependent on wavelength, to a full width of 1000 -
1400”. From the reflector surface construction and application of the
antenna tolerance theory we find that the measurable beam consists
of the diffracted beam, two underlying error beams which can be
explained from the panel dimensions, and a beam deformation mostly due
to large-scale transient residual thermal deformations of the telescope
structure. In view of the multiple beam structure of the 30-m telescope,
and of other telescopes with a similar reflector construction of
(mini-)panels and panel frames, we summarize the antenna tolerance
theory for the influence of several independent surface/wavefront
deformations. This theory makes use of different correlation lengths,
which in essence determine the independent error distributions, and
of the wavelength-scaling of the diffracted beam and of the error
beams. From the Moon scans we derive the parameters for calculation
of the 30-m telescope beam in the wavelength range 3 mm to 0.8 mm as
required for the reduction of astronomical observations, in particular
of extended sources. The parameters of the beam are primarily for the
time after July 1997 when the reflector was re-adjusted and improved
to the illumination weighted surface precision of sigma _T = 0.065 -
0.075 mm. In the Appendix we explain the choice for this analysis of
scans taken around New Moon and Full Moon.
---------------------------------------------------------
Title: The gain-elevation correction of the IRAM 30-m telescope
Authors: Greve, A.; Neri, R.; Sievers, A.
1998A&AS..132..413G Altcode:
The residual surface deformations of an optimized homologous radio
reflector produce an elevation dependent gain variation for which
astronomical observations must be corrected. For the IRAM 30-m telescope
we provide information, and an example, how to correct observations
of point-like and extended sources. We find agreement between the
gain-elevation dependence predicted from the finite element structural
calculations and radiometric measurements on the telescope.
---------------------------------------------------------
Title: VLBI observations of the galactic center source SGR A* at 86
GHz and 215 GHz
Authors: Krichbaum, T. P.; Graham, D. A.; Witzel, A.; Greve, A.; Wink,
J. E.; Grewing, M.; Colomer, F.; de Vicente, P.; Gomez-Gonzalez, J.;
Baudry, A.; Zensus, J. A.
1998A&A...335L.106K Altcode:
We have observed and detected Sgr A* with VLBI at 86 GHz and at 215 GHz
in March 1995. At 86 GHz the measured closure phase is close to zero,
consistent with a point-like or symmetric structure of 190 +/- 30 mu
as in size. At 215 GHz we have detected Sgr A* with a signal-to-noise
ratio of 6. This yields a tentative size estimate of 110 +/- 60 mu as
which, despite of a limited calibration accuracy and uncertainty in
the origin of the mm/sub-mm total flux density excess, lies well above
the scattering size of 20 mu as at this frequency. The intrinsic size
of Sgr A* thus appears to be 17 +/- 9 Schwarzschild radii for a 2.6 *
10^6 M_solar black hole.
---------------------------------------------------------
Title: Results of the SEST key programme: CO in the Magellanic
Clouds. VII. 30 Doradus and its southern H II regions
Authors: Johansson, L. E. B.; Greve, A.; Booth, R. S.; Boulanger,
F.; Garay, G.; de Graauw, Th.; Israel, F. P.; Kutner, M. L.; Lequeux,
J.; Murphy, D. C.; Nyman, L. -A.; Rubio, M.
1998A&A...331..857J Altcode:
We have mapped the (12) CO(1-0) emission from the 30 Doradus region in
the Large Magellanic Cloud with the Swedish-ESO Submillimetre Telescope
(SEST). The regions investigated include the central part of the 30
Dor nebula, and the southern Hii regions N 158C, N 159, and N 160. In
addition, a few prominent CO clouds have been studied in the (2-1)
and (3-2) transitions of CO. The southern area shows the strongest
(12) CO(1-0) emission, a factor of 3 higher than towards the central
part of 30 Dor. A non-LTE analysis of the CO emission from a sample
of clouds indicate kinetic temperatures between 10 and 50 K; the
highest temperatures are found close to the 30 Dor nebula. We have
estimated the CO-H<SUB>2</SUB> conversion factor for the two areas,
separately, under the assumption that the virial mass, determined
from CO parameters, reflects the total molecular mass. We find an
unexpectedly small difference between the two areas. This is explained
as a bias effect. Based on results collected at the European Southern
Observatory, La Silla, Chile
---------------------------------------------------------
Title: VLBI observations of CygnusA with sub-milliarcsecond resolution
Authors: Krichbaum, T. P.; Alef, W.; Witzel, A.; Zensus, J. A.; Booth,
R. S.; Greve, A.; Rogers, A. E. E.
1998A&A...329..873K Altcode:
We present new images of the two-sided VLBI-structure of the radio
galaxy CygnusA at 1.6GHz, 22GHz and 43GHz. The maps show the jet and
counter-jet of CygnusA on scales from ~ 400 to 0.1 milliarcseconds,
corresponding to projected sizes of ~ 300pc to 0.07pc. Our best 22GHz
image shows a small (few degree) misalignment of the VLBI-jets with
the kpc-jets, longitudinal oscillations of the jet's ridge line with
amplitudes of <= 0.6mas, and transverse oscillations of the jet's
width with amplitudes of 0.2 - 0.3mas. At distances of < 15mas from
the core, both jets expand at an opening angle of ~ 5^{\circ}. Between
22 and 43GHz the core has an inverted spectrum. The spectrum of the
jet appears steep, that of the counter-jet relatively flat. >From
two 22GHz observations we find evidence for apparent acceleration (from
0.1c to 0.7c) along the jet. The acceleration could be jet-intrinsic or
related to phase velocities. In the counter-jet structural variations
seem also to be present, but cannot accurately be determined. Between
1.6GHz and 43GHz the jet-to-counter-jet ratio R is frequency dependent
with a maximum of R =~ 5 near 5GHz and a smaller ratio of R =1 - 2 at
1.6GHz and 43GHz. This can be interpreted as an effect of absorption
by a partially opaque inclined absorber (e.g. a disk or a torus)
obscuring the counter-jet but not the jet. With an absorption corrected
intrinsically small jet-to-counter-jet ratio, CygnusA could be oriented
at a relatively large angle to the line of sight (theta > 80^{\circ},
for R <2) with jet velocities in the range 0.2 h <= beta <
1 (H_0= 100 * h(-1) km sec(-1) Mpc(-1) ).
---------------------------------------------------------
Title: The high-frequency compact radio structure of the peculiar
quasar 4C 39.25.
Authors: Alberdi, A.; Krichbaum, T. P.; Graham, D. A.; Greve,
A.; Grewing, M.; Marcaide, J. M.; Witzel, A.; Booth, R. S.; Baath,
L. B.; Colomer, F.; Doeleman, S.; Marscher, A. P.; Rogers, A. E. E.;
Schalinski, C. J.; Standke, K.
1997A&A...327..513A Altcode:
We present new high angular resolution images of the compact non-thermal
radio source 4C 39.25 obtained from VLBI observations at λ1.3cm,
λ7mm, and λ3mm wavelengths. These maps and Gaussian model-fits show
that the milli-arcsecond to sub-milliarcsecond structure of 4C 39.25
consists of a complex bent core-jet structure with embedded moving
and stationary VLBI components. Facilitated by the small observing
beams and high angular resolutions obtained at mm-wavelengths, we
measured the relative positions of the jet components with an accuracy
of a few hundred micro-arcseconds. This allows the detailed followup
of the ongoing merging process of a westward superluminally moving
component (b_) with a stationary component a_, located at ~2.9 mas
east of the putative core d_. In contrast to the other components
of the structure with steeper spectra, the westernmost component d_
exhibits an inverted spectrum peaking between λ7mm and λ3mm, thus
further supporting its identification as the VLBI core, self-absorbed at
longer wavelengths. From two VLBI maps obtained nearly simultaneously at
λ7mm and λ1.3cm, we made the first spectral index map of 4C 39.25 in
this wavelength regime. The main characteristics of the spectral index
distribution of the jet are pronounced changes of the spectral index
between orientations parallel and transverse to the jet axis. Near
the merging components a_ and b_ the spectral index steepens with
increasing separation from d_. However, in the bridge of emission c_,
which connects d_ with a_ and b_, the spectral index gradient has a
direction transverse to the jet axis, suggesting a frequency dependent
jet curvature and edge-brightening. A brief discussion of this behaviour
within current jet models is presented.
---------------------------------------------------------
Title: The Paschen decrement as a density indicator in MWC 349.
Authors: Thum, C.; Greve, A.
1997A&A...324..699T Altcode:
We present new observations of the Paschen series hydrogen recombination
lines in the circumstellar shell of MWC 349. We find the Paschen
decrement to be characteristic of a very high density plasma,
n_e_~10^8^cm^-3^, indicating the origin of the higher quantum number
Paschen lines in the dense corona of the circumstellar disk. The
strength of the masing hydrogen recombination α-lines detected
previously in the high density plasma of this source is strongly
dependent on n_e_, since the n_e_ for maximum amplification increases
systematically for decreasing quantum numbers n. The absence of gas with
n_e_ significantly higher than 10^8^cm^-3^ implies that the strength of
recombination α-line masers may peak near n=20 (λ=400μm) and that the
shorter wavelength transitions may mase only at reduced efficiency. The
good agreement over a large range of n between the observed and the
theoretical Paschen decrement shows that any departure from standard
recombination theory, possibly due to the strong IR radiation field
of the circumstellar disk, must be small.
---------------------------------------------------------
Title: Cassegrainian Gregorian-type null correctors for surface
measurements of radio telescope reflectors
Authors: Greve, A.
1997ApOpt..36.5283G Altcode:
The (sub)millimeter wavelength radio observatory of the next generation
will probably be an interferometer array of some 50 telescopes with
parabolic reflectors 10-15 m in diameter. At this scale of mass
production it is convenient to have at hand for workshop assembly a
reflector surface measurement technique that is precise and easy to
operate. We discuss the possibility of reflector measurements based on
10.6-μm CO2 laser interferometry using Cassegrainian/Gregorian-type
null correctors.
---------------------------------------------------------
Title: 215 GHz VLBI observations of bright Active Galactic Nuclei.
Authors: Krichbaum, T. P.; Graham, D. A.; Greve, A.; Wink, J. E.;
Alcolea, J.; Colomer, F.; de Vicente, P.; Baudry, A.; Gomez-Gonzalez,
J.; Grewing, M.; Witzel, A.
1997A&A...323L..17K Altcode:
We report the detection of 6 active galactic nuclei, and also
the marginal detection of the galactic center radio source SgrA*,
in 215GHz VLBI observations between the IRAM 30m telescope on Pico
Veleta and one 15m antenna of the IRAM Plateau de Bure interferometer
(~0.3mas fringe spacing). In this (second) 1.4mm VLBI-experiment we
find source dependent ratios between the total and correlated flux
densities in the range of 10-35%, indicating partly resolved brightness
distributions on sub-milliarcsecond scales. In view of the calibration
uncertainties and the limited uv-coverage at this high frequency this
needs further confirmation. The present detection limit of ~0.4-0.5Jy
opens the possibility for more extended 1.4mm VLBI experiments, in
particular with phased millimeter arrays.
---------------------------------------------------------
Title: Millimetre continuum measurements of extragalactic radio
sources. IV. Data from 1993-1994
Authors: Reuter, H. -P.; Kramer, C.; Sievers, A.; Paubert, G.; Moreno,
R.; Greve, A.; Leon, S.; Panis, J. F.; Ruiz-Moreno, M.; Ungerechts,
H.; Wild, W.
1997A&AS..122..271R Altcode:
Radio flux densities are presented for 118 extragalactic radio sources
monitored at 90, 142 and 230 GHz with the IRAM 30 m telescope during
1993-1994. For the most frequently observed sources we show light curves
including 30 m-measurements published in previous papers. Tables 1 and
4 are available electronically at the CDS via anonymous ftp 130.79.128.5
or at http://cdsweb.u-strasbg.fr/Abstract.html.
---------------------------------------------------------
Title: Millimeter VLBI at IRAM
Authors: Greve, A.
1997mvlb.work..107G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Coma correction of a wobbling subreflector.
Authors: Greve, A.; Lefloch, B.; Penalver, J.
1996ITAP...44.1642G Altcode:
Radio astronomical observations at millimeter wavelengths with
Cassegrain telescopes often use on-source/off-source measurements with
a wobbling subreflector to eliminate the influence of the Earth's
atmosphere. The tilt of the subreflector produces the required beam
throw, but also a coma-like wavefront deformation noticeable as a
degradation of the beam pattern and a reduction of the main beam
power. The authors demonstrate, with measurements made with the IRAM
30-m telescope at 1.3 mm wavelength (230 GHz) of the quasi-point-like
source Mars and the extended source Saturn, that it is possible to
eliminate (to a large extent) this wavefront deformation when using
a near-focus corrector, on the 30-m telescope conveniently located on
the co-rotating Nasmyth mirror.
---------------------------------------------------------
Title: On the consistency of solar limb darkening observations at
UV wavelengths (2000-3300A).
Authors: Greve, A.; Neckel, H.
1996A&AS..120...35G Altcode:
Limb darkening observations are important for the construction and
verification of solar model atmospheres. We investigate the consistency
of solar limb darkening data, published for the UV wavelength region
between 2000 and 3300A, from the comparison of F/I_0_ ratios based
either on direct limb darkening observations or on absolute irradiance
(F) and disk-center intensity (I_0_) measurements. There exists
a discrepancy between the limb darkening data of Moe & Milone
(1978ApJ...226..301M) and other, direct or indirect, limb darkening
observations.
---------------------------------------------------------
Title: VizieR Online Data Catalog: mm-monitoring of radio sources
IV. (Reuter+ 1997)
Authors: Reuter, H. -P.; Kramer, C.; Sievers, A.; Paubert, G.; Moreno,
R.; Greve, A.; Leon, S.; Panis, J. F.; Ruiz-Moreno, M.; Ungerechts,
H.; Wild, W.
1996yCat..41220271R Altcode:
Radio flux densities are presented for 118 extragalactic radio sources
monitored at 90, 142 and 230GHz with the IRAM 30m telescope during
1993-1994. For the most frequently observed sources we show light curves
including 30 m-measurements published in previous papers, Steppe et
al. (1988A&AS...75..317S; 1992A&AS...96..441S and and 1993,
Cat. <J/A+AS/102/611>) (2 data files).
---------------------------------------------------------
Title: NGC 1569: the molecular and ionized gas near the superluminous
star clusters A and B.
Authors: Greve, A.; Becker, R.; Johansson, L. E. B.; McKeith, C. D.
1996A&A...312..391G Altcode:
The starburst in the irregular galaxy NGC 1569 has produced two
superluminous star clusters A and B which strongly influence their
surroundings through UV radiation, stellar winds, supernova explosions,
and an outflow of very hot gas. Close to A and B is located the most
prominent HII region of NGC 1569; our CO observations indicate that it
contains ~ 2x10^6^M<SUB>sun</SUB>_ molecular gas which probably still
feeds star formation of its internal stellar cluster. When comparing
the molecular gas mass, calculated for Galactic conditions, and the
virial mass we obtain a conversion factor ~ 20 times higher than the
Galactic value. However, we believe that the molecular clouds near the
stellar clusters are not in kinematic equilibrium so that the virial
theorem does not apply; we therefore reject this conversion factor as
unrealistic. Our spectroscopic observations seem to indicate an optical
counterpart of the Hi cavity around A, though being smaller in extent,
and a surrounding shell of ionized gas of ~ 50 pc diameter. The compact
galaxy NGC 1705 contains a stellar cluster even brighter than A and
B. We did not detect CO in this galaxy.
---------------------------------------------------------
Title: The pointing of the IRAM 30-m telescope.
Authors: Greve, A.; Panis, J. -F.; Thum, C.
1996A&AS..115..379G Altcode:
The original pointing model of the IRAM 30-m millimeter wavelength radio
telescope is based on nine parameters which are updated from special
pointing measurements made approximately every two weeks. The pointing
models derived from these measurements provide a pointing accuracy
of 3.5" (rms) which, however, degrades slowly with time. Application
by the observer of instantaneous pointing corrections recovers the
inherently precise operation of the telescope. The data analyzed here
show that the number of pointing parameters used for the 30-m telescope
can be reduced to six because the astronomical positions of pointing
sources are today accurately known, and because the telescope does not
show hysteresis or long-term irreversible changes of its mechanical
behaviour so that the gravitational bending can be described by a
unique and time-independent function, as should be the case. There are
indications that the inclination of the azimuth axis is influenced by
seasonal thermal effects, which merit further monitoring for eventual
quasi real time correction. The other pointing parameters show random
variations in time which makes it difficult to trace any particular
source which sets their ultimate accuracy, although we suspect residual
thermal effects to be the main source of perturbation.
---------------------------------------------------------
Title: Near-focus active optics: An inexpensive method to improve
millimeter-wavelength radio telescopes
Authors: Greve, A.; Baars, J. W. M.; Peñalver, J.; LeFloch, B.
1996RaSc...31.1053G Altcode:
The application of active and adaptive optics allows the construction
of large diameter lightweight optical telescopes for observations
below the seeing limit of the atmosphere. Active wavefront correction
in a Cassegrain/Gregory-type radio telescope can be made with
a deformable main reflector or deformable subreflector. Here we
suggest the possibility of correcting spatially large-scale wavefront
deformations with a small size corrector located near the focus
of the telescope. Using representative examples of the Institut
de Radioastronomie Millimetrique (IRAM, Spain) 30-meter diameter,
millimeter-wavelength telescope, we calculate the improvement expected
from the correction of (1) the systematic component in homology
deformations, (2) the large-scale residual errors of a reflector
adjustment, and (3) the beam degradation experienced in observations
with a wobbling subreflector. The improvement in surface/wavefront
precision obtained from piston correction with a corrector of some 50
elements is of the order of 30%-40%. We investigate in particular the
systematic component of homology deformations, their representation
by low-order Zernike polynomials, and their elimination by near-focus
correction. We study in detail the homology deformations of the IRAM
30-m reflector.
---------------------------------------------------------
Title: Fe I lines in late type stellar UV spectra.
Authors: Greve, A.; McKeith, C. D.
1995A&A...302..165G Altcode:
It has been suggested that Fe I lines may constitute a major part of
the many absorption lines observed in the (near-UV) solar spectrum and
in those of late type stars. We use the table of Fe I lines recently
measured in the laboratory by Nave et al. (1994) and examine the
solar spectrum between 2756-2831A observed by us previously with the
highest spectral resolution to date, R=1.75x10^5^. We exploit this
existing observation since only such high spectral resolution allows
sufficient isolation of weak lines in an underlying haze of absorption
features. In this solar spectrum we detect ~90% of the tabulated
Fe I lines. Investigations of this kind are relevant, for instance,
to primordial abundances of beryllium and boron in late type metal
poor halo stars requiring complete model atmosphere line opacities
and discrimination of possible line blending. We illustrate the case
of Be with the spectrum of the late type star HD 165908 observed
with R=~5x10^4^.
---------------------------------------------------------
Title: 215 GHz VLBI observations: Detection of fringes on the 1147
KM baseline Pico Veleta-Plateau de Bure
Authors: Greve, A.; Torres, M.; Wink, J. E.; Grewing, M.; Wild, W.;
Alcolea, J.; Barcia, A.; Colomer, F.; de Vincente, P.; Gomez-Gonzalez,
J.; Lopez-Fernandez, I.; Graham, D. A.; Krichbaum, T. P.; Schwartz,
R.; Standke, K. J.; Witzel, A.; Baudry, A.
1995A&A...299L..33G Altcode:
In a VLBI test experiment between the IRAM 3Om telescope at Pico
Veleta, Spain, and one 15-m telescope of the IRAM interferometer on
Plateau de Bure, France, we detected fringes at 215 GHz with signal
to noise ratios between 6 8 and 10.2. On this 1147km long distance,
of 0.28-0.43 milli arcseconds projected fringe spacing at 215 GHz,
we have 8 independent detections of the sources 3C273, 3C279 and
2145+067 The clock and fringe rates at 215 GHz are consistent with
those derived from VLBI measurements at 86 GHz made at the beginning
or end of the 215 GHz observations. The coherence time at 215 GHz were
of the order of 10 seconds, most probably limited by the atmosphere.
---------------------------------------------------------
Title: The outflow in the halo of M 82.
Authors: McKeith, C. D.; Greve, A.; Downes, D.; Prada, F.
1995A&A...293..703M Altcode:
New observations of emission and absorption lines along M 82's minor
axis yield detailed radial velocity-position curves tracing the blowout
of the superwind from the starburst region. The new velocity data
provide good evidence for the acceleration of the wind in the energy
input region (z<300pc), for the wind becoming supersonic about
300pc above and below the galactic plane, and tending to a constant
velocity in the free wind zone at z>300pc. Inflexion points in the
velocity curves suggest that the blowout region has an hourglass shape,
that is, the profile is cylindrical for z<300pc, and flares out
to a conical shape for z>300pc. While most of the line emission
comes from ionized gas moving on the surfaces of the blowout cones,
some of it may be scattered, appearing near the systemic velocity. The
stellar Ca II IR absorption lines appear near the systemic velocity at
all distances along the minor axis. These lines may come mainly from
late-type stars in the disk, with the radiation scattered by dust in
the halo. Although a contribution from scattered light is definitely
present, any explanation for the emission lines wholly in terms of
scattered radiation from dust in a giant bipolar reflection nebula is
immediately ruled out by a) the large blue shifts (-300 to -450km/s)
relative to the systemic velocity of the galaxy, b) the monotonic
variations of the velocity as a function of height above the galactic
plane, c) the non-shifted, non-split, scattered stellar CaII IR lines,
and d) the variation of the extinction-independent [SII] line ratios,
which indicate a rapid decrease of electron density with height above
the galactic plane. The superwind model accounts for these facts both
qualtitatively and quantitatively.
---------------------------------------------------------
Title: Spectroscopic studies of the disk and halo of M82.
Authors: McKeith, C.; Greve, A.; Downes, D.; Prada, F.
1995ASIC..469..325M Altcode: 1995osd..conf..325M
No abstract at ADS
---------------------------------------------------------
Title: Astigmatism in reflector antennas: measurement and correction
Authors: Greve, A.; Lefloch, B.; Morris, D.; Hein, H.; Navarro, S.
1994ITAP...42.1345G Altcode:
We investigate astigmatism in Cassegrain antennas from cross scans
through in-and-out-of-focus diffraction images of extended radio
sources. The use of extended sources is of interest for large (mm
wavelength) telescopes where the bright planets subtend a substantial
fraction of the beam. The experimental and theoretical results
presented here refer to the IRAM 30-m telescope and measurements at
7.3 mm-1.3 mm wavelength; however, extrapolation to other telescopes
is evident. We report on an experiment to correct the astigmatism
(phase) at a position close to the focal plane of the telescope, i.e.,
the flat surface of the corotating Nasmyth mirror.
---------------------------------------------------------
Title: The exciting star of the small bubble N 120A in the Large
Magellanic Cloud
Authors: Laval, A.; Gry, C.; Rosado, M.; Marcelin, M.; Greve, A.
1994A&A...288..572L Altcode:
UV characteristics of the star BI 141 show that it is the exciting
star of the nebula N 120A of the LMC. We determine its UV spectral
classification as O_9.5_I and we derive the terminal velocity and
mass-loss rate of its stellar wind, in agreement with the usual
values found for galactic supergiants of the same spectral type. The
energetic balance between the power of the stellar wind and the
measured energetic input into the surrounding gas shows that the wind
is largely the dominant factor for driving the bubble. The best model
for the sustained bubble is the model with conservation of energy,
(nonradiative shocked stellar winds). The discrepancy between the
visible spectral classification B_3_I and the UV classification opens
the questions of either the multiplicity or the variability of BI 141,
and of its stellar wind.
---------------------------------------------------------
Title: NGC 1569: identification from CA II infrared line spectra of
the objects A, B as superluminous star clusters
Authors: Prada, F.; Greve, A.; McKeith, C. D.
1994A&A...288..396P Altcode:
We present blue and near-infrared spectroscopic data which provide
evidence that the stellar-like objects (called A and B) in the nucleus
of NGC 1569 are star clusters. The Ca II infrared triplet absorption
lines and the slope of the spectral continuum reveal that the star
cluster B is in the red supergiant phase of the cluster evolution
at an age of 12 Myr, while the star cluster A is in the blue star
phase at an age of 13-20 Myr. Evidence for a stellar condensation
is also found within the large H II region close to A as indicated
by the Ca II triplet present in its near-infrared spectrum. We give
reddening-corrected emission line ratios for this H II region.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Outflow in M82 halo (McKeith+,
1995)
Authors: McKeith, C. D.; Greve, A.; Downes, D.; Prada, F.
1994yCat..32930703M Altcode:
Not Available (2 data files).
---------------------------------------------------------
Title: Disk brightness temperature of the planets at 43 GHz (and 43
GHz flux densities of some continuum sources).
Authors: Greve, A.; Steppe, H.; Graham, D.; Schalinski, C. J.
1994A&A...286..654G Altcode:
We have used the MPIfR 43 GHz (7 mm) Schottky receiver, installed in
1991 on the IRAM 30-m telescope for VLBI observations, for flux density
measurements of several planets in comparison with several Galactic
and extra-galactic continuum sources, using as calibration standards
the sources W3OH and NGC 7027. The disk brightness temperatures of
the planets are derived from these flux densities.
---------------------------------------------------------
Title: Design parameters and measured performance of the IRAM 30-m
millimeter radio telescope.
Authors: Baars, J. W. M.; Greve, A.; Hein, H.; Morris, D.; Penalver,
J.; Thum, C.
1994IEEEP..82..687B Altcode:
The "Millimeter Radio Telescope" (MRT) is operated by the Institute for
Radio Astronomy in the Millimeter range (IRAM) and is located at 2850-m
altitude in the Sierra Nevada, near Granada, Spain. The authors compare
the design computations with the characteristics of the telescope,
derived from several years of operation and optimization. The success
of the design is demonstrated by the observational experience.
---------------------------------------------------------
Title: An investigation of extinction diagnostics towards the
Orion Nebula.
Authors: Greve, A.; Castles, J.; McKeith, C. D.
1994A&A...284..919G Altcode:
We present for the Orion nebula long-slit spectroscopic observations
of emission lines in the wavelength regions 10 000-11 000 A and
3700-7330 A. These wavelength regions contain the corresponding
multiplet lines of common upper atomic level of hydrogen P_6_-H_6_
(= P<SUB>gamma</SUB>_ -H<SUB>delta</SUB>_) and P_7_-H_7_ (=
P<SUB>delta</SUB>_-H<SUB>epsilon</SUB>_) and of [S II] at 10 300
A and 4072 A. From these lines the extinction A_V_ towards the
Orion nebula is derived with minimal reliance on recombination
line model calculations. We find good internal agreement for
the extinction derived from the corresponding hydrogen and [S II]
lines, except for deviations of the order of 20-30% for data based on
H<SUB>epsilon</SUB>_ and P<SUB>delta</SUB>_, where deblending of the
H<SUB>epsilon</SUB>_ line may be uncertain by this amount and the flux
of the P<SUB>delta</SUB>_ line contains a similar error. There exists
good agreement with the extinction derived from the other Paschen and
Balmer line combinations. We also discuss in particular the method of
extinction determination proposed by Allen (1979). However, we find
no advantage from this over the other methods based on Paschen-Balmer
lines and corresponding [S II] lines, neither from a greater precision
achieved nor from the observational requirements.
---------------------------------------------------------
Title: Wavelength-dependent Kinematics in the Dusty Inclined Galaxy
NGC 2146
Authors: Prada, F.; Beckman, J. E.; McKeith, C. D.; Castles, J.;
Greve, A.
1994ApJ...423L..35P Altcode:
We present measurements of the apparent rotation curves of the dusty
inclined spiral NGC 2146 taken using conventional long-slit spectroscopy
in the red and near-infrared. The curve measured in Hα emission shows,
with respect to that observed in [S III] λ9069, a series of dips in
velocity which coincide in positions with dips in the intensity of
Hα, and with the dust lanes evident in broad band images. A more
detailed quantitative comparison, including a previously published
velocity curve in Brγ (Hutchings et al. 1990), using a schematic
model, supports the hypothesis that dust is causing the Hα/[S III]
discrepancies and highlights the need to measure rotation curves of
inclined galaxies as far into the infrared as techniques permit. The
λ9069 [S III] emission reveals a zone in expansion at 190 pc from the
nucleus (previously detected in Brγ but at lower spectral resolution
and with consequently limited velocity diagnostics) whose kinematics and
energetics are well explained in terms of an expanding "superbubble"
due to a starburst. Finally we suggest, from the invariance of the
velocity curve with wavelength at nucleocentric radii greater than 1500
pc that our observations imply very limited observable dust extinction
in the outer parts of the disk of NGC 2146.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Millimeter continuum of
extragal. sources III. (Steppe+ 1993)
Authors: Steppe, H.; Paubert, G.; Sievers, A.; Reuter, H. P.; Greve,
A.; Liechti, S.; Le Floch, B.; Brunswig, W.; Menedez, C.; Sanchez, S.
1994yCat..41020611S Altcode:
Not Available (2 data files).
---------------------------------------------------------
Title: MM Observations of Active Galactic Nuclei with a High
Sensitivity VLB-Array
Authors: Schalinski, C. J.; Witzel, A.; Krichbaum, T. P.; Graham,
D. A.; Standke, K. J.; Rogers, A. E. E.; Doleman, S.; Zensus, J. A.;
Greve, A.; Bååth, L. B.; Booth, R. S.
1994cers.conf...45S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Millimeter continuum measurements of extragalactic radio
sources. III.
Authors: Steppe, H.; Paubert, G.; Sievers, A.; Reuter, H. P.; Greve,
A.; Liechti, S.; Le Floch, B.; Brunswig, W.; Menedez, C.; Sanchez, S.
1993A&AS..102..611S Altcode:
This paper presents a catalog of 118 extragalactic radio sources
observed at 90, 150 and 230 GHz from November 1990 to the end of
1992. The figures contain flux densities for 83 sources from both
previous catalogs (Steppe et al. 1988, Steppe et al. 1992) and this
paper.
---------------------------------------------------------
Title: First 43 GHz VLBI-observations with the 30-m radio telescope
at Pico Veleta.
Authors: Krichbaum, T. P.; Witzel, A.; Graham, D. A.; Standke, K. J.;
Schwartz, R.; Lochner, O.; Schalinski, C. J.; Greve, A.; Steppe, H.;
Brunswig, W.; Butin, G.; Hein, H.; Navarro, S.; Penalver, J.; Grewing,
M.; Booth, R. S.; Colomer, F.; Ronnang, B. O.
1993A&A...275..375K Altcode:
A three station VLBI experiment performed at 43 GHz (λ= 7 mm
wavelength) demonstrated the superior performance of the 30-m
millimeter radio telescope of IRAM at Pico Veleta especially for
mm-VLBI observations. Although primarily intended as a technical
test, these first 43 GHz VLBI observations with Pico Veleta yielded
new scientific results. A first VLBI map of Cygnus A (=3C 405) at 43
GHz shows a core-jet-like structure of ~4 mas length, with several
compact components embedded. The map also shows some evidence for
jet bending near the core of about {DELTA}P.A. = 5-15^deg^. The
apparent subluminal motion in the "inner jet" of 3C 84 (= NGC 1275)
is confirmed and seems to show (apparent) acceleration along the jet
from 21 000 km s^-1^ close to the nucleus to 114000 km s^-1^ at ~4 mas
separation from the VLBI-core. The absence of any detectable counter-jet
requires either a direct orientation of the jet towards the observer
or a pronounced asymmetry between jet and counter-jet. In 3C 345 the
apparent superluminal motion along bent trajectories of two recently
ejected jet components (C6 and C7) was further monitored. Inspection
of their paths indicates trajectories largely different from each other
and from those of their precursors. These results and the detection of
other extragalactic objects and galactic SiO-maser sources show that
the participation of the IRAM 30-m radio telescope in VLBI observations
at millimeter wavelengths greatly enhances the detection threshold
and imaging capabilities of mm-VLBI.
---------------------------------------------------------
Title: Global photometric structure of the Orion nebula.
Authors: Greve, A.; van Genderen, A. M.; Augusteijn, Th.
1993A&AS...99..577G Altcode:
We present Walraven V BLUW photometric observations of the Orion
nebula. For an idealized radial-symmetric nebula the brightness
distribution decreases exponentially with distance from the Trapezium
stars. The integrated brightness and color is calculated.
---------------------------------------------------------
Title: Rotation of stars and gas in M 82.
Authors: McKeith, C. D.; Castles, J.; Greve, A.; Downes, D.
1993A&A...272...98M Altcode:
New observations of near IR emission and absorption lines along M 82's
major axis yield radial velocity-position curves that differ markedly
from those derived from lines at visible wavelengths. For the central
disk we find identical rotation for the gas and the stars, contrary
to earlier results. The rotation derived from emission and absorption
lines at visible wavelengths refer to outer regions of the galaxy
since at these wavelengths the central disk is obscured by dust.
---------------------------------------------------------
Title: The 86 GHz VLBI test with Pico Velat: first detection of
quasar 3C454. 3 at 3 mm wavelength
Authors: Schalinski, C.; Greve, A.; Grewing, M.; Steppe, H.; Graham,
D.; Krichbaum, T.; Witzel, A.; Alberdi, A.; Baath, L.; Booth, R. S.;
Colomer, F.
1993sara.conf..184S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Thermal behavior of millimeter wavelength radio telescopes
Authors: Greve, Albert; Dan, Michel; Penalver, Juan
1992ITAP...40.1375G Altcode:
Thermal protection applied to the IRAM 15-m mm-wavelength and 30-m
mm-wavelength telescopes and their thermal behavior are discussed. The
design of the passive/active thermal protection of these telescopes is
based on dynamic time-dependent model calculations, which are explained
and compared with in situ recorded temperatures of the telescope
components. It is demonstrated that dynamic model calculations are
capable of reproducing the observed thermal behavior of significant
structural components with sufficient precision. It is pointed out
that continued monitoring of the thermal behavior may lead to further
improvements the performance of a telescope.
---------------------------------------------------------
Title: Submillimeter Spectrum and Dust Mass of the Primeval Galaxy
IRAS 10214+4724
Authors: Downes, D.; Radford, J. E.; Greve, A.; Thum, C.; Solomon,
P. M.; Wink, J. E.
1992ApJ...398L..25D Altcode:
We measured with the IRAM 30 m telescope the continuum flux of the
extremely luminous primeval galaxy IRAS 10214+4724 at a wavelength of
1.2 mm. This is the longest wavelength at which this galaxy's thermal
continuum radiation has been detected; at z = 2.286, it corresponds to
a rest wavelength of 370 microns. From the entire continuum spectrum
we estimate a dust temperature of 80 K, and from the optically thin
radiation at 370 microns (rest frame) we find a dust mass of 2.5 X 10^8^
h^-2^ M_sun_. For the H_2_ mass of 1 X 10^11^ h^-2^ M_sun_ implied by
the CO line luminosity, this yields a ratio of the mass of gas (H_2_ +
He) to warm dust of 500, which is surprisingly normal for a galaxy at z
= 2.3. It is the same value as observed in the central regions of nearby
luminous galaxies that have solar metallicity. The ratio of observed CO
and 370 microns (restframe) luminosities in 10214 + 4724, essentially
the gas-to-dust mass ratio, is the same as in nearby galaxies. Hence,
In this galaxy, most of the heavy elements have already been produced,
at nearly present-day abundances.
---------------------------------------------------------
Title: The IRAM interferometer on Plateau de Bure.
Authors: Guilloteau, S.; Delannoy, J.; Downes, D.; Greve, A.; Guelin,
M.; Lucas, R.; Morris, D.; Radford, S. J. E.; Wink, J.; Cernicharo, J.;
Forveille, T.; Garcia-Burillo, S.; Neri, R.; Blondel, J.; Perrigourad,
A.; Plathner, D.; Torres, M.
1992A&A...262..624G Altcode:
The IRAM interferometer on Plateau de Bure has three 15 m diameter
antennas presently equipped with low noise receivers for the 80-115 GHz
band. Baselines extend 160m north-south and 288 m east-west. There are
two digital cross-correlators, a wide band continuum correlator and
a narrow band spectral correlator. The instrument's high sensitivity
is a result of its relatively large antennas.
---------------------------------------------------------
Title: HCN in the center of the galaxy IC 342.
Authors: Downes, D.; Radford, S. J. E.; Guilloteau, S.; Guelin, M.;
Greve, A.; Morris, D.
1992A&A...262..424D Altcode:
We have mapped HCN(1-0) line emission from the center of the galaxy
IC 342 with the IRAM interferometer at 2.7" resolution. By comparing
this HCN map with other molecular line maps of similar resolution,
we have made the first determination of molecular line ratios on a
scale of 20 pc in a massive galaxy other than our own. In the five
main clouds within 100 pc of IC 342's nucleus, the CO(1-0)/HCN(1-0)
intensity ratio is 7 +/- 2 and is at least twice as high farther out in
the mini spiral arms. In the central region, the line intensity ratios
of ^13^CO(1-0)/HCN(1-0) and HCN(1-0)/NH_3_ are both ~ 2. We have also
detected 3.4 mm continuum radiation near the center of the galaxy at a
level of 27 mJy. Comparison with other maps shows the 3.4 mm continuum
is free-free emission rather than thermal radiation by dust. The number
of ionizing photons is similar to that in our Galactic center. Since the
free-free continuum is associated with only one of the dense molecular
clouds traced by the HCN, most of the molecular clouds in the center of
IC 342 do not show any massive star formation activity. The gas in the
molecular clouds is probably heated by turbulent dissipation rather than
starlight. Since both the HCN(1-0) and the far IR radiation come from
much smaller regions than the ^12^CO(1-0) the HCN is better correlated
with the FIR radiation than is ^12^CO, but neither HCN nor CO trace
star formation. The global L_FIR_/M(H_2_) ratio is only an indirect
indicator of the efficiency of star formation in the center of IC 342.
---------------------------------------------------------
Title: Optical Extinction in HII Regions and Nearby Bright Galaxies
Authors: Castles, J.; McKeith, C. D.; Greve, A.
1992IrAJ...20..191C Altcode:
Observations with the 1.5 m telescope at ESO, Chile, and the 4.2 m
WHT at RGO, La Palma, of galactic HII regions and three galaxies were
made to evaluate the potential for A<SUB>upsilon</SUB> determination,
using pairs of lines from transitions from common upper levels, and
separated by a large wavelength interval. Spectral lines from the near
UV to the near IR are shown to be accessible with modern blue-coated
CCD detectors.
---------------------------------------------------------
Title: Extinction towards 30 Doradus (LMC) derived from common upper
level P-gamma/H-delta and P-delta/H-epsilon line ratios.
Authors: Greve, A.; Castles, J.; McKeith, C. D.
1991A&A...251..575G Altcode:
We have used the ratios Pγ/Hδ and Pδ/H{epsilon of corresponding
hydrogen multiplet lines (which originate from the same upper levels)
to derive the extinction A_v_ in the direction of 30 Doradus in the LMC.
---------------------------------------------------------
Title: Galaxy kinematics from ISIS spectra
Authors: Castles, J.; McKeith, C. D.; Greve, A.
1991VA.....34..187C Altcode:
The ISIS spectrograph on the 4.2 m WHT was used to observe three
galaxies NGC 2146, NGC 1569, and NGC 3034 (M82). Rotation curves
along the major axes of these galaxies are presented. For NGC 3034,
the rotation curve derived using the relatively new technique for
measuring stellar motion from one of the the CaII IR triplet ( ∼8550
Å) absorption lines is compared with those for the ionized gas motion
measured from H<SUB>α</SUB> and [NII] (6583 Å) emission lines. The
line splitting with slit oriented along the minor axis of NGC 3034
covering 4 arc min. is examined.
---------------------------------------------------------
Title: The Dense Molecular Core of ARP220
Authors: Radford, S. J. E.; Delannoy, J.; Downes, D.; Guélin, M.;
Guilloteau, S.; Greve, A.; Lucas, R.; Morris, D.; Wink, J.
1991IAUS..146..303R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Structure of the disk of M 82.
Authors: Goetz, M.; Downes, D.; Greve, A.; McKeith, C. D.
1990A&A...240...52G Altcode:
We present new observations of H, He, O, N and S emission lines and
Hα and Na D absorption lines parallel to the major axis in the central
region of the galaxy M 82, and derivations of the Balmer decrements and
the visual extinction. Whereas the absorption lines trace the rotation
curve of stars in the disk of M 82, the emission lines come from H II
regions in the inner and outer starburst zones. These emission lines
show two velocity components separated by 270 km s^-1^ in the central
region, over 50" (760 pc) parallel to the major axis. We interpret the
two velocity components as H II regions in the galactic disk (component
I), and the starburst wind (component II). In the current picture of
M 82, the starburst region consists of the brighter 10 micron zone
of diameter 100 pc (+/- 5"), and extends out to the central CO zone
of diameter 500 pc (+/- 17"). Our data show that the molecular ring
is surrounded by a split emission line zone of diameter 760 pc (+/-
25") near the major axis, inside of which is presumably the blowout of
the hot superwind. The double structure in the strong emission lines
in this zone is related to the much weaker split line system seen by
other observers in the filaments out of the plane of M 82. Beyond this
blowout zone is a wider, quiescent Hα zone of diameter 1500 pc (+/-
50"), surrounded by the outer disk, whose rotation can be traced in
stellar absorption lines.
---------------------------------------------------------
Title: Scanning interferometer observations of the shell N 186E in
the Large Magellanic cloud.
Authors: Rosado, M.; Laval, A.; Boulesteix, J.; Georgelin, Y. P.;
Greve, A.; Marcelin, M.; Le Coarer, E.; Viale, A.
1990A&A...238..315R Altcode:
The velocity field and the Hα flux of the large shell N 186E of the
LMC are measured over a 7' x 7' field, covering most of the filamentary
structure. The radial velocity field appears to be contamined by faint
blue-shifted and red-shifted emission which confirms the presence of
H I slabs along the line of sight. The remaining gas in N 186E does
not show high velocity expansion motions (25 km s^-1^), much less
than found inside the similar but smaller bubble N 185. The recently
detected exciting sturs are sufficient to explain the ionization of N
186E, although none of them is located close to the centre. The density
inside the filaments is produced by weak shocks, where as the circular
shape and the size of the shell indicate homogeneity of the preshock
material, An intense interaction is found at the dense border between
N 186E and the young neighbouring SNR, N 186D. N 186E is probably an
old SNR, now being ionized by internal stars.
---------------------------------------------------------
Title: Dust in emission nebulae of the LMC derived from photometric
reddening of stars.
Authors: Greve, A.; van Genderen, A. M.; Laval, A.
1990A&AS...85..895G Altcode:
We present VBLUW photometric observations of stars in emission nebulae
of the LMC (N 4AB, N 11AB, N 12, N 48ACB, N 57C, N 77, N 79ABDE, N 81,
N 83AB, N 163, N 195, N 214C, 30 Dor). The luminosities and extinctions
A_v_ of the stars are derived. We find agreement between the average
photometric extinction of the nebulae and the extinctions derived
from the Balmer line decrement measured by Caplan and Deharveng (1985,
1986). The photometric extinction, are shown in the CO map of the LMC
(Cohen et al, 1988).
---------------------------------------------------------
Title: CCD spectroscopy of P<SUB>γ</SUB>(10939),
P<SUB>δ</SUB>(10049) and corresponding Balmer lines in 30 Doradus.
Authors: Greve, A.; McKeith, C. D.; Castles, J.
1989Msngr..57...56G Altcode: 1989Mgr....57...56G
Understanding the physical and dynamical evolution of galactic and
extragalactic H11 regions requires a knowledge of the dust component
and its distribution. To date the extinction Av has been derived by
various methods: optical and infrared line ratios, comparison of radio
and emission line fluxes, stellar photometry, etc. In particular the
intensity ratios of the strong and spectroscopically easily accessible
Balmer lines Halpha, Hbeta are frequently used to derive Av via their
decrement. Since these lines originate from different upper levels, the
interpretation of the observed line ratios requires recombination line
model calculations (cf. Osterbrock 1974) which in many extragalactic
cases have failed to give consistent results (Ward et al. 1987, Malkan
1983, Rieke and Lebofsky 1981). This difficulty can be avoided by
using multiplet line ratios originating from the same upper level so
that the theoretical line ratios depend primarily on their relative
transition probabilities.
---------------------------------------------------------
Title: The Swedish-ESO submillimeter telescope (SEST).
Authors: Booth, R. S.; Delgado, G.; Hagstrom, M.; Johansson, L. E. B.;
Murphy, D. C.; Olberg, M.; Whyborn, N. D.; Greve, A.; Hansson, B.;
Lindstrom, C. O.; Rydberg, A.
1989A&A...216..315B Altcode:
The Swedish-ESO 15 m diameter, submillimetre wavelength telescope on
La Silla is now complete. Here we describe the salient features of
the telescope and the first instrumentation as well as results from
commissioning tests. The telescope reflector surface has been set
within 65 microns of the ideal paraboloid and the aperture efficiency
at 100 GHz is about 60%. A pointing accuracy of approximately 3" rms
has been measured in both azimuth and elevation. Results of the first
astronomical measurements are presented.
---------------------------------------------------------
Title: Extinction towards the Orion nebula derived from
P-gamma/H-delta and SII 1.04 mu-m/4071 A line ratios.
Authors: Greve, A.; Goetz, M.; McKeith, C. D.; Barnett, E. W.
1989A&A...215..113G Altcode:
Using the Orion nebula as typical example of H II regions, it is
demonstrated that the differential extinction can be derived precisely
from (P-gamma)/(H-delta) and forbidden S II blue and IR line ratios
observed with long-slit CCD spectroscopy. This spectroscopic imaging
technique allows a correct elimination of perturbing atmospheric sky
emission lines in the IR wavelength region, so that this technique
may become a useful diagnostic tool for other H II regions.
---------------------------------------------------------
Title: Study of Bubbles in the Large Magellanic Cloud
Authors: Laval, A.; Rosado, M.; Boulesteix, J.; Georgelin, Y. P.;
Marcelin, M.; Cahalo, D.; Greve, A.; Larsen, J.; Viale, A.
1989rdmc.conf..151L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Interaction between a stellar wind and the ionized gas in N120
(LMC)
Authors: Laval, A.; Rosado, M.; Boulesteix, J.; Georgelin, Y. P.;
Marcelin, M.; Greve, A.; Larsen, J.; Viale, A.
1989LNP...350..194L Altcode: 1989IAUCo.120..194L; 1989sdim.conf..194L
No abstract at ADS
---------------------------------------------------------
Title: An investigation of the micro variations of highly luminous
OBA type stars (alpha Cygni variables). VII. The two interacting O
type eclipsing binaries UW CMa = HD 57060 and 167971.
Authors: van Genderen, A. M.; van Amerongen, S.; van der Bij, M. D. P.;
Damen, E.; van Driel, W.; Greve, A.; van Heerde, G. M.; Latour, H. J.;
Ng, Y. K.; Oppe, J.; Wiertz, M. J. J.
1988A&AS...74..467V Altcode:
VBLUW photometry of two interacting O type binaries UW CMa and HD
167971 are presented and discussed. The light and colour curves of
UW CMa (P = 4<SUP>d</SUP>.39336) show evidence of plasma streams in
the system. The light amplitude of the optical micro variations likely
originating mainly on the O8.5 I component, is about twice as large as
for non distorted stars of the same temperature. The micro variations
superimposed on the light curve of HD 167971 (P = 3<SUP>d</SUP>.3218),
likely originating on the more distant component of this triple system,
are of a normal size. Convincing colour variations during the binary
revolution are detected. The size of these amplitudes are corrected
for the light of the companion(s).
---------------------------------------------------------
Title: Photometric reddenings of stars in emission nebulae of the
MagellanicClouds.
Authors: Greve, A.; van Genderen, A. M.; Laval, A.; van Driel, W.;
Prein, J. J.
1988A&AS...74..167G Altcode:
We present VBLUW observations of stars in emission nebulae of the SMC
(N 66, N 83, N 90) and the LMC (N8, N9, N 11E, N23, N43, N48, N59, N84,
N 148, N 159, N 160A, N 185, N 186). The stellar population (colour
indices, luminosities) and the extinction in the central regions of
the nebulae are derived. We find several stars, in particular in N
159 and N 160A, with extinctions A_V_ > 1.5 mag. Intrinsically more
luminous, hence more massive, stars, or groups of stars, are located
in the regions of the highest extinction.
---------------------------------------------------------
Title: Thermal control of the IRAM 30-m millimeter radio telescope
Authors: Baars, J. W. M.; Hooghoudt, B. G.; Greve, A.; Penalver, J.
1988A&A...195..364B Altcode:
The performance of millimeter wavelength telescopes may be critically
impaired by temperature differences, which cause structural
deformations larger than those due to gravity and wind. Model
calculations show that a temperature uniformity of the telescope
structure of about 1 K is required. For the 30-m millimeter radio
telescope that is realized by thermal insulation of the telescope
and temperature control of the reflector support structure and the
quadrupod, allowing full performance independent of time of day or
season. A description of the control system is given together with
measured performance data. The additional cost of the thermal control
amounts to 10 percent of the total cost of the telescope. The increase
in availability with unimpaired characteristics is estimated at a
factor of 1.5-2. Calculations with a detailed thermal model are also
in accordance with the measurements. Thus temperature effects can be
included numerically in the structural design and be controlled to
eliminate thermally induced deformations.
---------------------------------------------------------
Title: The Swedish-ESO Submillimeter Telescope (SEST)
Authors: Booth, R. S.; Delgado, G.; Hagstroem, M.; Johansson, L. E. B.;
Murphy, D. C.; Olberg, M.; Whyborn, N. D.; Greve, A.; Hansson, B.;
Lindstroem, C. O.
1988STIN...8927605B Altcode:
The Swedish-ESO Submillimeter Telescope (SEST) is a 15 m telescope,
which can operate at wavelengths down to 0.8 mm, built on the European
Southern Observatory (ESO) site of La Silla, in the Chilean Andes, at
an altitude of 2300 m. It is the only large submillimeter telescope in
the Southern Hemisphere. The main technical features of the telescope
and observing system, and the results of the commissioning tests by
the team in Chile are described. The telescope reflector surface has
been set within 65 micrometers vms of the ideal paraboloid, and the
aperture efficiency at 100 GHz is about 60 percent.
---------------------------------------------------------
Title: Solar Flux Spectra at 2000-3000 a High Resolution
Authors: Greve, A.
1988iue..prop.3255G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: VBLUW photometry of emission nebulae.
Authors: Greve, A.; van Genderen, A. M.
1987A&A...174..243G Altcode:
Observed VBLUW colours of emission nebulae of the SMC, LMC, and the
Orion nebula are reconstructed from published emission line ratios
and theoretical H and 2-photon continua. The authors discuss colour
corrections for internal reddening, scattered star light (in particular
for the Orion nebula), and stellar backgrounds. The calculations
reproduce the observed colours in the (B-U)/(B-L) diagram and indicate a
correlation of (B-U) with the [O II] 3727/Hβ line ratios. After a more
detailed empirical confirmation, this correlation may eventually be
used as a diagnostic indicator of emission nebulae. The authors also
give colours for a few galactic planetary nebulae, and a tentative
interpretation of the measurements.
---------------------------------------------------------
Title: The stars and gas in the region of N 63 A (LMC).
Authors: Laval, A.; Greve, A.; van Genderen, A. M.
1986A&A...164...26L Altcode:
N 63A is located in the cluster NGC 2030 of the LMC. From VBLUW
observations of some cluster stars the authors derive A<SUB>V</SUB> =
0.6 mag reddening in the direction of N 63A; the age of the cluster is
estimated as ≡4×10<SUP>6</SUP>yr. VBLUW observations indicate the
western knot of N 63A to be excited by an 05-9 main sequence star. The
north-eastern and southern knots form the known SNR. Fabry-Perot
observations indicate a velocity range of 100 - 300 km s<SUP>-1</SUP>
for the SNR gas.
---------------------------------------------------------
Title: VBLUW photometry of solar-type stars.
Authors: Greve, A.; van Genderen, A. M.
1986A&A...160..392G Altcode:
VBLUW photometric observations of 35 solar-type stars are presented
and discussed in terms of abundance, T<SUB>eff</SUB> and gravity
(log g). Using the empirical transformation between the VBLUW and UBV
systems, for four stars being very similar to the sun the authors derive
(B-V) = 0.656±0.011.
---------------------------------------------------------
Title: Reflector surface measurements of the IRAM 30-m radio telescope
Authors: Greve, A.
1986IJIMW...7..121G Altcode:
Surface measurements of the IRAM 30 m radio reflector made with a
theodolite-laser-tape system are described. The results obtained with
this survey system agree with holography measurements made at 22 GHz
(Morris 1985).
---------------------------------------------------------
Title: Solar Flux Soectra at 2000-3000 Angstrom, High and Low
Resolution
Authors: Greve, A.
1986iue..prop.2715G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: VBLUW photometry of the stars and nebulosity of N 70 in
the LMC.
Authors: Greve, A.; van Genderen, A. M.
1985A&A...148..397G Altcode:
Photometric VBLUW data are given for the stars and nebulosity of N 70
in the LMC. The data for the central cluster stars, an OB association
mainly of main sequence stars, confirm earlier color determinations
and spectral types. Located in the direction of the shell region of the
nebula, a number of supergiants which may partly be associated with N
70 are found. The photometry for three of these stars give extinctions
of A(VJ) = 3m. Also found for a few stars in other nebulae of the LMC,
this amount of extinction - if of interstellar origin - does not agree
with the interstellar gas to dust ratio of the LMC. The extinction
may be produced in circumstellar dust shells.
---------------------------------------------------------
Title: Status report on the IRAM 30-m telescope.
Authors: Thum, C.; Morris, D.; Greve, A.
1985ESOC...22...57T Altcode: 1985sma..work...57T
Apart from commissioning the new SIS receivers and the bolometer, the
technical activities for the rest of this year include derivation of
a pointing model at high frequencies. Further work includes tests of
switching techniques and an extension of the data reduction software and
documentation. From September onward, the telescope will be scheduled
50 per cent of the time for visitor programs which, for the time being,
have to originate from the IRAM member countries (90 per cent) or from
the telescope host country, Spain (10 per cent).
---------------------------------------------------------
Title: Photometry of AO 0538-66 during an active and subsequent
inactive state.
Authors: van Paradijs, J.; van Amerongen, S.; de Kool, M.; Pakull,
M.; Deul, E. R.; Lub, J.; Greve, A.
1984MNRAS.210..863V Altcode:
The authors present the results of photometric observations of the
optical counterpart of the recurrent X-ray transient A0538-66. Three
outbursts were observed in 1982 April and May. During the period 1982
October - 1983 February the source did not show outbursts. Combining
their data with those of Densham et al. the authors find evidence for
a secular decrease of the size of the outbursts throughout a period of
activity. The interoutburst UBV properties of A0538-66 likewise show a
progressive change. During the off-state A0538-66 shows small-amplitude
variability, similar to that observed in some 'normal' Be stars. In the
(V, B-V) and (U-B, B-V) diagrams both these variations and the secular
variations of the previous interoutburst data lie along tracks which
appear to be connected.
---------------------------------------------------------
Title: Observations of the emission nebulae S 188 and S 274 at 2.7
and 5 GHz.
Authors: Salter, C. J.; Greve, A.; Weiler, K. W.; Birkle, K.;
Dennefeld, M.
1984A&A...137..291S Altcode:
The two morphologically similar nebulae S188 and S274 have been mapped
in the radio continuum at 2.7 and 5 GHz. The sources seem to have
thermal spectra and the new data effectively rule out that either
or both are shell-type supernova remnants. It is demonstrated that a
number of distance-independent parameters of the nebulae are closely
similar and all present evidence indicates that both are old planetary
nebulae. On this hypothesis, the distances of the nebulae are estimated
from the radio data. A number of other parameters of the objects are
considered in the light of these distances.
---------------------------------------------------------
Title: Comparison of Ultraviolet Spectra from Solar Type Stars
Authors: Greve, A.; Wamsteker, W.
1984SoPh...94....3G Altcode:
We compare high-resolution spectra from the Sun and the four solar-type
stars 16 Cyg A, 16 Cyg B, HD 32008, HD 34411 obtained with IUE in
the wavelength range 2650-2930 Å. The comparison is made for peak
intensities between absorption lines. At the level of accuracy of
the IUE observations, the stars 16 Cyg A, 16 Cyg B, HD 34411 are
indistinguishable from the Sun, in particular the MgII resonance line
profiles are identical. HD 32008 is not a solar analog but is evidently
of late G to early K spectral type.
---------------------------------------------------------
Title: A Cassegrain type null-corrector for surface tests of parabolic
microwave reflectors
Authors: Greve, A.
1984IJIMW...5..761G Altcode:
The design of Cassegrain-type interferometric null-correctors for
steep parabolic reflectors (as used for microwave and IR observations)
is examined analytically. The optical principle is explained and
illustrated, and the surface contour is derived. It is demonstrated
that physically meaningful solutions exist, and the practicality of a
device using metallic aspheric surfaces and 10.6-micron light from a
CO2 laser is discussed. Surface roughness less than about 1.5 microns
rms and accuracy about 1 mm are required.
---------------------------------------------------------
Title: Prediction of wet air refraction at microwaves (research note)
Authors: Greve, A.
1984IJIMW...5..315G Altcode:
Radiosonde data have been used to calculate the actual wet air
refraction which results from the combined effect of the dry air and
water vapor components, in an attempt to establish, for long periods and
large seasonal changes, correlations with atmospheric qualities that
are measurable at the surface. Attention is given to the possibility
of wet air refraction prediction on the basis of surface pressure
and temperature measurements, integrated water vapor, and microwave
atmospheric emission data.
---------------------------------------------------------
Title: Atmospheric water vapour measurements at Zelenchukskaya
(U.S.S.R.) and La Silla (Chile).
Authors: Sherwood, W. A.; Schultz, G. V.; Greve, A.
1983InfPh..23..109S Altcode:
Direct measurements of atmospheric precipitable water vapour are
presented for Zelenchukskaya at the site of the 6 m telescope. The data
may be compared with previous data and with indirect determinations
based on extinction measurements at 1 mm interpreted in terms of
experimental water vapour transmittance measurements. It is shown
that the cosecant law is justified in practice. Indirect measurements
of water vapour at the European Southern Observatory, La Silla show
that precipitable water vapour may be less than 2 mm for ≡50% of the
southern hemisphere winter time. A low value of 0.6-0.7 mm is reported.
---------------------------------------------------------
Title: Correlation of surface humidity and integrated atmospheric
water vapour determined from infrared measurements.
Authors: Greve, A.
1983InfPh..23...59G Altcode:
For four European mountain sites the author correlates values
of precipitable water vapour with simultaneous data on surface
humidity. For the particular sites, the correlation of daily values
is too poor to allow reliable predictions of water vapour required
for astronomical observations.
---------------------------------------------------------
Title: Absolute photometry of the Crab Nebula
Authors: Greve, A.; van Genderen, A. M.
1982A&A...115...79G Altcode:
The observations discussed were made on December 6 and 7, 1980,
using the Walraven VBLUW simultaneous photometer with the Leiden
90-cm light collector (ESO, La Silla, Chile). For each observation,
a 16-arcsec diaphragm was used, and the integration time was 192 s. The
astrophysical quantities derived for M 1 from the broad passband VBLUW
observations are found to agree with other observations. This agreement
is believed to derive from a determination of the contribution of
emission line radiation in the observations. It is pointed out that
the photometric system may be used to observe, with smaller diaphragms
(greater than about 5 arcsec), small-scale details of M 1, for example,
the synchrotron emission of the wisps and the line emission at positions
where spectral data are given by Woltjer (1958).
---------------------------------------------------------
Title: Determination of the atmospheric water vapour content above
La Silla and the prospects for FIR observations
Authors: Sherwood, W. A.; Greve, A.
1982esoi.work..173S Altcode:
The results of a survey to estimate the amount and effects of
precipitable water vapor (pwv) are reported, with an emphasis on
the influence on FIR observations. The measurements were made at La
Silla for 24 hr/day for nine days in July 1981. An increase in pwv
was detected only once during daytime, and when rises were observed
the temperature was low; pwv and humidity were once seen to decrease
simultaneously. Use of a 350 micron filter encountered an atmospheric
transmissivity of 34 percent. Standard planets were used to calculate
the extinctions due to the water vapor strengths in the IR. The
implementation of 24 hr/day monitoring of pwv with an IR hygrometer is
recommended to permit transferring observations to lower wavelengths
in the presence of a dryer atmosphere.
---------------------------------------------------------
Title: Book reviews
Authors: Page, D. E.; Pick, M.; Kresák, L.; Reijnen, G. C. M.;
Cameron, A. G. W.; Schuurmans, Cornelius J. E.; Ya Marov, Mikhail;
Goldberg, B.; Kaiser, T. R.; Lemaire, J.; Sehnal, L.; Elsässer,
H.; Valniček, B.; de Graaff, W.; Pacini, Franco; Rohlfs, K.; de
Landtsheer, A. C.; Zhongolovich, I. D.; de Jager, C.; Greve, A.;
Ruprecht, J.; Tayler, R. J.; Kockarts, G.; Axford, W. I.; Tabor, H.;
Bolle, H. J.; Kaldis, E.; Reijnen, Gijsbertha C. M.; De Loore, C.;
Kleczek, J.; Murray, C. A.; Wallenquist, Åke
1981SSRv...28..105P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Metrology of the Effelsberg 100 meter radio reflector.
Authors: Greve, A.
1981ZVer..106..308G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Quality evaluation of radio reflector surfaces
Authors: Greve, A.; Hooghoudt, B. G.
1981A&A....93...76G Altcode:
Three rms values of sigma:sigma<SUB>n</SUB> were considered to
represent the geometrical quality of the surface for the evaluation of
radio reflector surfaces. The effective rms-value sigma<SUB>TP</SUB>
represents the electrical quality of the reflector; this quantity and
the corresponding surface weighting function must be taken into account
in design calculations, adjustment procedures, and in comparisons with
the radio gain measurements. The Effelsberg 100 m antenna is used as
an example of a steep parabolic reflector.
---------------------------------------------------------
Title: Supernova Remnants in the LMC and SMC
Authors: Greve, A.
1981iue..prop..882G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Book Review - Radio Recombination Lines
Authors: Shaver, P. A.; Greve, A.
1981SSRv...28..112S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Modulated laser surface surveying system for mm-wavelength
radio telescopes.
Authors: Greve, A.; Harth, W.
1981SPIE...36..110G Altcode:
For high precision (50 micron) surface measurements of a mm-wavelength
radio reflector we have developed a modulated laser (He-Ne 632 nm,
mod. freq. 1.7 GHz) distance ranger and an angular measuring system
of 0.4" accuracy. We give test results of the system.
---------------------------------------------------------
Title: UV Opacities of Solar-Type Stars
Authors: Greve, A.
1981iue..prop..881G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Astrophysical interpretation of the lam lam 1200-7300
angstrom emission line spectrum of a filament in the CYG Loop
Supernova remnant.
Authors: Dodorico, S.; Dennefeld, M.; Benvenuti, P.; Dopita, M. A.;
Greve, A.
1980A&A....92...22D Altcode:
An IUE spectrum of a filament in the Cygnus Loop supernova remnant
obtained with the low resolution, long wavelength camera, has been
combined with earlier far UV and optical data to obtain a complete
spectral coverage between 1200 and 7350 Å. The observed continuum is
fully understood as a combination of free-free emission, recombination
and hydrogen two photon emission, reinforced by collisional excitation
to the 2S½ level. <P />The emission lime spectrum is, in general, well
interpreted in the framework of a shockwave model of moderate velocity
(v<SUB>s</SUB>=90 km/s) and depleted abundances. <P />The unexpected
weakness of the C II λ1335 Å line may be due to scattering in the
filament seen as an edge on sheet, or, less likely, owing to absorption
in the intervening interstellar medium, indicates a column density
of interstellar C II of ≃2.5 × 10<SUP>14</SUP> cm<SUP>-2</SUP>
toward the remnant.
---------------------------------------------------------
Title: The formation of the Mg II resonance line wings in the solar
atmosphere (II).
Authors: Greve, A.
1980A&A....90..231G Altcode:
Synthetic LTE profiles of the Mg II resonance lines computed for
the HSRA, VAL, and 'Ca II and Mg II' model atmospheres are compared
with profiles of the average quiet sun in the gamma wavelength range
2760-2820 A at the radial positions of 1.0, 0.6 + or - 0.06, and 0.43 +
or - 0.01. The expression for the total opacity as a function of the
height is derived; these opacity functions reproduce the observed
local continuum intensities at gamma 2660 and 2940 and the adopted
wavelength averaged limb darkening curve. The most appropriate value
of the abundance of Mg and the factor applied to the collisional
broadening is derived from the best fit of the calculated profiles;
the comparison of the computed and observed profiles shows that none
of the one-component static model atmospheres for the average quiet
sun reproduces the center-to-limb variations for the central parts of
the MG II profiles.
---------------------------------------------------------
Title: Absolute fluxes, equivalent width and centre-to-limb profiles
of the solar Mg II resonance lines (I).
Authors: Greve, A.; McKeith, C. D.
1980A&A....90..224G Altcode:
For the average quiet Sun we derive from high resolution Fabry
Perot-echelle spectrograms profiles of the Mg II resonance lines
in the wavelength region 2760 Å ≲ λ ≲ 2820 Å for the radial
positions 1.0 ≧ = μ ≧ 0.995, 0.60±0.06 and 0.43±0.10. The
profile of a plage region near the disc centre is also presented. <P
/>From the absolute flux calibrated observations of Kachalov and
Jakovleva (1962), and Tousey et al. (1974), we derive the Mg II flux
profile in the wavelength region 2660 Å ≲ λ ≲ 2940 Å. The
Minnaert-Houtgast method is applied to the far wings of this profile
in order to determine the undisturbed continuum level. Related to
this continuum the equivalent width of the Mg II resonance lines is
83 Å. <P />For the region 2770 Å ≲ λ ≲ 2820 Å a wavelength
averaged limb darkening curve is derived. The Mg II profiles are
calibrated using a combination of this limb darkening curve and the
low spectral resolution flux profile. Our profile for the disc centre
agrees in shape and absolute intensity with Kohl and Parkinson's
(1976) recent observation. <P />In the Appendix we generalize the
Minnaert-Houtgast method for a blend of two strong multiplet lines
and a linear variation of the continuum intensity.
---------------------------------------------------------
Title: Methods for the analysis of stellar spectra veiled by lines
(III).
Authors: Greve, A.; Zwaan, C.
1980A&A....90..239G Altcode:
UV spectrograms of the sun and of Alpha CMi are analyzed to investigate
the effects of finite spectral resolution in the interpretation
of stellar spectra veiled by lines. The recorded completeness of
intrinsic spectral detail is examined by means of the ruggedness
parameter of Ivanov and Salman-Zade (1976). Solar spectrograms of
approximately 0.03 A resolution are a good representation of the true
spectral distribution. The power of the Minnaert-Houtgast method for
tracing line wings and establishing the local 'continuum' background
in spectra crowded with lines is demonstrated.
---------------------------------------------------------
Title: Strehl number degradation by large-scale systematic surface
deviations.
Authors: Greve, A.
1980ApOpt..19.2948G Altcode:
For the particular case of circular zones, the corresponding image
degradation is derived. The equations obtained lead to a general
expression for the on-axis intensity of the degradation image, i.e.,
the Strehl number, for large-scale surface deviations (SD). Random
deviations (RD) are compared with SD. It is shown that the quasi-rms
value of SD has the same optical significance as the rms value of RD.
---------------------------------------------------------
Title: The Influence of Spectral Resolution on Line Blending and
Wavelength Positions in the Solar Ultraviolet Spectrum
Authors: Greve, A.; McKeith, C. D.
1980SoPh...65..405G Altcode:
For representative sections of the solar UV spectrum (λ 2765 Å-λ
2790 Å, λ 2765 Å-λ 2805 Å) the line density and the accuracy of
wavelength positions of absorption features are derived as function
of the spectral resolution. In low resolution spectrograms unresolved
blends may shift intrinsic wavelength positions of absorption lines
by amounts up to a few tenths of the spectral resolution.
---------------------------------------------------------
Title: On the Zeeman splitting of high N recombination lines
Authors: Greve, A.; Pauls, T.
1980A&A....82..388G Altcode:
The Zeeman splitting pattern of high-n alpha and beta lines of H II,
He II, and Cu II ions is calculated rigorously. All allowed transitions
are taken into account, together with the corresponding strengths for
Russel-Saunders coupling, and the allowed fine structure transitions,
the corresponding Lande factors, and the strengths are obtained by the
application of selection rules. It is found that for principle quantum
numbers between 30 and 300, identical hydrogen-like Zeeman triplets are
obtained for the alpha and beta lines of the three ions, with a Lande
factor generally equal to 1 and triplet components of equal strength.
---------------------------------------------------------
Title: On the hyperfine structure of the mesospheric water vapour line
(22 GHz).
Authors: Greve, A.
1978JATP...40.1029G Altcode:
Model calculations of the hyperfine structure splitting of the
mesospheric water vapor line at 22.2351 GHz are examined. While
the vapor line was observed with the 120-ft Haystack antenna in
conjunction with a cooled ruby maser, it is suggested that detection
of the hyperfine structure splitting will be extremely difficult
unless the constitution of the atmosphere deviates considerably at
high altitudes from presently accepted models. Hyperfine structure
calculations for two mixing ratios are presented. The mesospheric
water vapor line, seen in emission and absorption against the sun,
has a typically pressure-broadened profile.
---------------------------------------------------------
Title: Further evidence for downflow in the solar atmosphere.
Authors: Greve, A.
1978SoPh...58..287G Altcode:
Downflow velocities of the higher atmospheric layers of the Sun are
derived from wavelength measurements of the Mg II core absorption.
---------------------------------------------------------
Title: Off-axis aberration of achromatic Schmidt correctors.
Authors: Greve, A.
1978Optik..50..235G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The water vapour content in the western European atmosphere
obtained from infrared measurements.
Authors: Greve, A.
1978InfPh..18..127G Altcode:
We report on measurements of the water vapour content in the western
European atmosphere obtained from infrared attenuation measurements,
made during a site survey for a millimetre-wave radio observatory.
---------------------------------------------------------
Title: Achromatic Schmidt corrector plates for the near infrared.
Authors: Greve, A.
1978InfPh..18....7G Altcode:
The paper demonstrates the advantages of near infrared achromatic
Schmidt systems, which eliminate spherical aberration at two
wavelengths, and give a residual spherical aberration which fulfils
the Strehl/Rayleigh criterion. The theory is illustrated by a few
numerical examples.
---------------------------------------------------------
Title: The ultraviolet solar spectrum 2756Å - 2831Å - Identification
of absorption lines
Authors: Greve, A.; McKeith, C. D.
1977A&AS...30..387G Altcode:
A list of atomic spectral lines and semi-empirical gf values published
by Kurucz and Peytremann (1975) allows increased and improved
identifications of solar UV absorption lines previously observed in
the range 2756 1 A. The compiled table of identifications with listed
gf values and excitation potentials is relevant to line blanketing
estimates in model atmosphere calculations of late-type stellar
spectra. Key words: solar UV spectrum - identifications
---------------------------------------------------------
Title: Absolute photometry of the supernova remnants N 49 and N 64
A in the Large Magellanic Cloud.
Authors: Greve, A.; van Genderen, A. M.
1977A&A....59..267G Altcode:
Summary. We present five-colour photometric (Walraven system)
observations of the supernova remnants N 49 and N 63 A of the Large
Magellanic Cloud. The observations of N 49 indicate an optically thin,
filamentary shell. The photometric observations allow a calibration
of the spectroscopic observations of N 49, published by Osterbrock and
Dufour (1973); absolute surface intensities of the spectral lines can
be derived. A detailed comparison of the observations of N 49 with
predictions from shock wave models is made and good agreement is
found. As a particular conclusion, the interstellar medium density
near N 49 is found to be . Key words: supernova remnants photometry
absolute spectral line intensities shock wave model
---------------------------------------------------------
Title: High n solar radio recombination lines.
Authors: Greve, A.
1977SoPh...52..423G Altcode:
For a representative set of atmospheric and atomic parameters we
determine the strengths of solar dielectronic recombination lines
originating in ions with Z ⩽ 6 at frequencies of ≳70 GHz. We
compare the line strengths derived here with those calculated by
Berger and Simon (1972) and find that our values for representative
ions with Z≲3 are lower by a factor 10<SUP>2</SUP>-10<SUP>3</SUP>,
being mainly the result of the inclusion of the electronic pressure
broadening. We outline the requirements for the detection of lines,
which must establish an upper limit of at least ≈10<SUP>-5</SUP>
for the line to continuum ratio.
---------------------------------------------------------
Title: Die Justierung der Reflektorflächen großer Radioteleskope.
Authors: Greve, A.
1977S&W....16..122G Altcode:
The importance of an accurate agreement of the characteristics
of the actual reflector surface with the properties of the ideal
surface in the case of optical and radio telescopes is considered. The
obtainable surface quality of the reflectors of optical telescopes and
the methods used for testing the surface characteristics are briefly
discussed. A description is given of the procedures which can be used
for a correction of the surface characteristics of the aluminum-steel
reflectors of radio telescopes. The required mathematically defined
surface characteristics are obtained with the aid of approaches
involving the adjustment of the sectional elements. Advantages and
drawbacks of the various available methods are evaluated.
---------------------------------------------------------
Title: The Brightness Distribution over the Moon's Disk at 6 cm
Wavelength
Authors: Hirth, W.; Butz, M.; Fuerst, E.; Greve, A.
1976Moon...15..317H Altcode:
On November 27, 1974, a map of the Moon was obtained at 6 cm wavelength
with the 100-m-telescope in Effelsberg. The high angular and favourable
temperature resolution allowed an interpretation of the observed
brightness distribution. The dominant feature of the brightness
distribution is the centre-to-limb variation, particularly noticeable
in the direction of the poles. The exponentα of the commonly adopted
cos<SUP> α </SUP> (ψ)-law, describing the temperature variation
across the lunar disk, is determined asα ≃ 0.4. The North-South
variation of the lunar surface temperature is estimated to be 30%;
the depth of penetration (L <SUB>e</SUB>) of electromagnetic waves of
6 cm wavelength is found to beL <SUB>e</SUB> ≃ 17 m.
---------------------------------------------------------
Title: Fluorescence lines excited by the Mg II resonance lines (II).
Authors: Greve, A.
1976A&A....51..313G Altcode:
The influence of spectral resolution on the full width at the base
of the emission core of the Mg II k line (2795.5 A) is determined
by comparing solar observations with convolved profiles, and a
width-magnitude relation is derived. The relation is used to predict
the behavior of fluorescence lines excited by Mg II emission cores in
Ke, Me, and N stars.
---------------------------------------------------------
Title: Achromatic Schmidt corrector plates.
Authors: Greve, A.
1976OptLT...8..137G Altcode:
Two types of achromatic Schmidt corrector plate are described; both
give an on-axis Strehl number S ⪆ 0.8 over an extended wavelength
region. It is found that this specification can only be achieved
by combining a positive and a negative plate and by restricting the
speed ratio D/N<SUP>3</SUP> of the system. The theory is illustrated
by numerical examples.
---------------------------------------------------------
Title: The Zeeman Broadening of High n Solar Recombination Lines
Authors: Greve, A.
1975SoPh...44..371G Altcode:
The Zeeman broadening of high n lines is derived. While in areas of
the quiet Sun with field strengths of ≈1 G the upper boundary of
the observable frequency region of recombination lines is defined by
electron impact broadening, in active regions with field strengths
≳25 G the Zeeman broadening will shift this boundary to higher
frequencies. The frequency region most favourable for observations
is derived and the corresponding Doppler, electron impact and Zeeman
broadening are discussed. The strengths of the recombination lines
obtained in earlier calculations is reduced when one considers besides
the Doppler broadening the electron impact and Zeeman broadening
also. The frequency region favourable for observations is compared
with the atmospheric transparency of the microwave region; it is
found that observations require at least high altitude stations or
space-based platforms. Details of using the Zeeman broadening of high
n recombination lines for mapping (coronal) magnetic fields are given.
---------------------------------------------------------
Title: Schmidt systems for the near-infrared.
Authors: Greve, A.
1975InfPh..15..239G Altcode:
The formulae which define the parameters (focal ratio, field) of
a seeing-limited Schmidt system are given. Near-infrared (5000 to
15,000 A) Schmidt systems are discussed for nine different corrector
plate materials.
---------------------------------------------------------
Title: High n Emission and Absorption Lines of the Sun (II)
Authors: Greve, A.
1975SoPh...40..329G Altcode:
Considering the electronic pressure broadening of highn solar
recombination lines, an upper wavelength limit of the observable
region of possible lines is derived. The reason that no lines have
been observed is discussed.
---------------------------------------------------------
Title: Eine semiempirische Entfaltungsmethode an scharfen Gradienten
einer Strahlungsflußverteilung
Authors: Butz, M.; Greve, A.; Hachenberg, O.; Hirth, W.
1975MitAG..36..116B Altcode:
Problems regarding the discussion of errors occur when a deconvolution
approach utilizing the Fourier transform or other methods is
employed in the case of sharp gradients. A description is given of a
semiempirical method for which an evaluation of the error can be more
easily performed. The method involves a comparison of the measured
flux distribution with the flux distribution obtained in the case of
the convolution of an ideal box-like brightness distribution.
---------------------------------------------------------
Title: Achromatic Schmidt corrector plates.
Authors: Greve, A.
1975Optik..42...87G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Fluorescence lines excited by the Mg II resonance doublet.
Authors: Greve, A.
1974A&A....36..135G Altcode:
Summary. Possible fluorescence lines, excited by absorption lines
coinciding with the Mg n resonance line emission, are listed. We point
out that two further absorption lines of Fe I and Zr I may possibly
affect the shape of the Mg ii 2795.52 A line of oc ORI, since in the
visible spectrum of Ke, Me and N stars a fluorescence counterpart of
these lines is observed with reasonable strength. Key words: stellar
Mg II emission - fluorescence lines
---------------------------------------------------------
Title: The ultraviolet solar spectrum 2756 Å 2831 Å
Authors: Greve, A.; McKeith, C. D.
1974SoPh...37....3G Altcode:
The ultraviolet spectrum of the Sun over the region 2756 Å to 2813 Å
has been observed with a spectral resolution of 0.016 Å during the
rocket flight of an interferometer spectrograph. Reduced wavelengths
and identifications are presented together with a spectral atlas of
the recorded region.
---------------------------------------------------------
Title: High n Emission and Absorption Lines of the Sun
Authors: Greve, A.
1974SoPh...36...85G Altcode:
Due to the expected peaks of the b<SUB>n</SUB> curves of ions in the
chromosphere-corona transition region and the corona, high n transition
lines change from emission to absorption in the wavelength region from
≈ 1/2 mm for elements in a low state of ionization, to ≈ 2 mm for
elements in a high state of ionization. The observational consequences
are discussed. We believe that lines have not yet been found because
the observations were made too close to the wavelength region where
the lines change from emission to absorption and therefore disappear.
---------------------------------------------------------
Title: Diffractional image degradation due to radial, parabolic
temperature distributions in a lens.
Authors: Greve, A.; Hunt, G. C.
1974Optik..40..332G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Strehl number of degraded diffraction patterns.
Authors: Greve, A.; Hunt, G. C.
1974Optik..40...18G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A remark on turbulence and `production' limited telescopes
Authors: Greve, A.
1973SoPh...29..263G Altcode:
The image degradation due to residual surface inaccuracies of the main
optical element of a telescope is compared with the image degradation
due to atmospheric turbulence.
---------------------------------------------------------
Title: High resolution ultraviolet solar spectra in the region 2765
2822 Å
Authors: Greve, A.; McKeith, C. D.; McKeith, N. E.
1973SoPh...28..289G Altcode:
Wavelengths and identifications of the near ultraviolet solar spectrum
are presented. The data were obtained during the rocket flight of an
interferometer spectrograph with a spectral resolution of 0.03 Å.
---------------------------------------------------------
Title: High-resolution ultraviolet solar spectra in the region 2765 -
2822 Å.
Authors: Greve, A.; McKeith, C. D.; McKeith, N. E.
1973MNRAS.161..289G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Das solare UV-Spektrum in der Umgebung der Mg II-Resonanzlinien
Authors: Greve, A.; McKeith, C. D.; McKeith, N. E.
1973MitAG..34..107G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: 25 Jahre Beobachtungen der solaren UV Strahlung.
Authors: Greve, A.
1973Stern..49..212G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Een teleskoop voor het infrarood.
Authors: Greve, A.
1973HemD...71...62G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: 25 jaar UV-waarnemingen van de zon.
Authors: Greve, A.
1973HemD...71..170G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On the Size Distribution of Turbulent Elements in the Earth's
Atmosphere
Authors: Greve, A.
1972SoPh...24..243G Altcode:
Solar scintillation measurements made by Wessely and Mitchell are used
to derive the size distribution of turbulent elements in the Earth's
atmosphere. Assuming a stationary state of the Earth's atmosphere,
the production rate of the turbulent elements is calculated.
---------------------------------------------------------
Title: Nieuwe grote optische telescopen.
Authors: Greve, A.
1972HemD...70..219G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On the center to limb variation of the separation of the Mg
ii, H<SUB>2</SUB> and K<SUB>2</SUB> emission peaks
Authors: Greve, A.
1971SoPh...16..328G Altcode:
From observations of the center to limb variation of the emission
peaks of the MgII, H and K lines the optical thickness of the emitting
layer for a simplified geometrical model has been calculated to
be ≈ 300. The source function was approximated by a second order
polynomial. The turbulent velocities of the emitting layer are found
to be ≈ 6.8 km/sec, in agreement with other observations.
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Title: De 1.52 meter-spiegeltelescop van de Universiteits-Sterrenwacht
van Wenen.
Authors: Greve, A.
1971HemD...69..320G Altcode:
No abstract at ADS
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Title: High quantum number emission and absorption lines of Fe V
viii, Fe xv, O iii, O vii of the sun
Authors: Greve, A.
1970SoPh...15..380G Altcode:
No abstract at ADS
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Title: Ca II en Mg II, H- en K-lijnen van de zon.
Authors: Greve, A.
1970HemD...68..157G Altcode:
No abstract at ADS
