scholarly journals VLA Observations of Planetary Nebulae at the Galactic Centre

1983 ◽  
Vol 103 ◽  
pp. 423-424
Author(s):  
R. Gathier ◽  
S.R. Pottasch ◽  
W.M. Goss ◽  
J.H. van Gorkom
Keyword(s):  
New Mexico ◽  
Detection Limit ◽  
Selection Effect ◽  
Planetary Nebulae ◽  
Radial Velocities ◽  
Galactic Centre ◽  
Large Array ◽  
Very Large Array ◽  
Instrumental Resolution

The Very Large Array (VLA) in Socorro, New Mexico, has been used to measure the 6 cm continuum flux densities and the angular sizes of 42 planetary nebulae (PN) in the direction of the galactic centre (GC). These were all optically confirmed PN for which the radial velocities (and positions on the sky) make it very likely that they are close to the GC. With a detection limit of about 1 mJy, 34 PN were detected. Their flux densities range from 2 to 100 mJy. Initially we used a configuration of the VLA with an instrumental resolution of 1″. About 80% of the detected PN could be clearly resolved with this resolution. The unresolved PN were observed again with a configuration of the VLA that has a resolution of 0″.4. For all but one of the 34 detected PN we could determine reliable angular sizes. The inferred total ionized masses range from < 0.01 to ~ 0.5 M⊙, assuming a distance to the GC of 9 kpc. The results argue strongly against the use of the Shklovsky method for distance determinations. Previous measurements of PN at the GC showed that their luminosities were substantially higher than those for nearby PN (Pottasch, 1980). The luminosity distribution of the PN in our sample is broader towards lower luminosities (up to the detection limit of the observations), but the luminosities are still high compared with nearby PN. We interpret this as a selection effect: by studying only optically confirmed PN, the intrinsically brightest PN are selected.

VLA Observations of a Sample of Low-Brightness 6.7 GHz Methanol Masers

2017 ◽  
Vol 13 (S336) ◽  
pp. 311-312
Author(s):  
Luca Olmi ◽  
Esteban D. Araya ◽  
Jason Armstrong
Keyword(s):  
New Mexico ◽  
Star Formation ◽  
Far Infrared ◽  
Large Array ◽  
Very Large Array ◽  
Early Stages ◽  
Methanol Masers ◽  
Infrared Sources ◽  
Massive Cores

AbstractIn 2014 we conducted a survey for 6.7 GHz methanol masers with the Arecibo Telescope toward far infrared sources selected from the Hi-GAL catalog of massive cores. We found a number of sources with weak 6.7 GHz methanol masers, possibly indicating regions in early stages of star formation. Here we describe the results of follow-up observations that were conducted with the Very Large Array in New Mexico to characterize this new population of “weak” 6.7 GHz methanol masers.

scholarly journals A VLA Radio Continuum Survey of Planetary Nebulae

1989 ◽  
Vol 131 ◽  
pp. 60-60
Author(s):  
A. Zijlstra ◽  
S. R. Pottasch ◽  
C. Bignell
Keyword(s):  
High Resolution ◽  
Planetary Nebulae ◽  
Radio Continuum ◽  
Large Array ◽  
Very Large Array

With the Very Large Array it is now possible to make high resolution radio continuum maps with sensitivity less than a milliJansky in an observation of only 5 minutes. We have used this so-called snapshot capability to measure about 400 PN north of declination −35. Most of the measurements were carried out at 6 cm. Some of the stronger sources were observed at several frequencies. Most sources were detected, however many nebulae were too weak to map in detail. The resolution ranges from 1.5″ to 1′, depending on the size of the PN. The selected PN have sizes in the range from 4″ to 6′.

scholarly journals Future Spectral Line Research with the VLA

1980 ◽  
Vol 87 ◽  
pp. 627-629
Author(s):  
K. J. Johnston
Keyword(s):  
New Mexico ◽  
Spectral Line ◽  
Radio Astronomy ◽  
Molecular Species ◽  
Large Array ◽  
Astronomy Observatory ◽  
Very Large Array ◽  
Radio Astronomy Observatory ◽  
Optical Telescopes

The Very Large Array (VLA) is presently being constructed on the Plains of San Augustine near Socorro, New Mexico by the National Radio Astronomy Observatory. The purpose for which this instrument is being constructed is to produce “radio images” of resolution comparable to that of large optical telescopes. There have already been several “test” observations, some successful, using the partially completed instrument to study the molecular species of OH, H2O, and NH3 with wide bandwidths (200-1500 kHz).

scholarly journals OH/IR Stars Near the Galactic Centre

1983 ◽  
Vol 103 ◽  
pp. 542-543
Author(s):  
H.J. Habing ◽  
F.M. Olnon ◽  
A. Winnberg ◽  
H.E. Matthews ◽  
B. Baud
Keyword(s):  
Spatial Distribution ◽  
High Velocity ◽  
Surface Brightness ◽  
Velocity Dispersion ◽  
Galactic Centre ◽  
Galactic Rotation ◽  
Red Giants ◽  
Large Array ◽  
Very Large Array ◽  
Ir Stars

We have detected 34 OH/IR stars within 1 degree of the galactic centre by their OH emission line at 1612 MHz (18 cm) using the Effelsberg 100 m telescope and the Very Large Array. The spatial distribution and the distribution of the radial velocities show that practically all stars are within 150 pc from the Galactic centre, and that the number of foreground objects is very small. The projected distribution of the stars is similar to that of the surface brightness at 2.4 μm. Since the 2.4 μm radiation is supposed to be due to red giants, the OH/IR stars are probably members of the same population. The stars have considerable random velocities (velocity dispersion in one coordinate of 150 ± 50 km s−1), but show general Galactic rotation. The high velocity dispersion is remarkable for objects of this population.

scholarly journals Radio Observations of Planetary Nebulae

1983 ◽  
Vol 103 ◽  
pp. 61-68
Author(s):  
P. F. Scott
Keyword(s):  
Planetary Nebulae ◽  
General Assembly ◽  
Large Array ◽  
Radio Telescopes ◽  
Radio Observations ◽  
Very Large Array ◽  
Separate Section ◽  
General Review ◽  
Full Operation

A discussion of radio observations for the period up to 1979 forms part of the general review given at the 1979 IAU General Assembly by Terzian (1980) and I shall be concerned here mainly with later results. With the advent of improved radio telescopes and techniques, in particular the coming into full operation of the Very Large Array (VLA), there has been an increasing interest in compact and proto-planetary nebulae and I shall discuss these observations in a separate section of this review.

scholarly journals VLA Observations of the Galactic Centre at 74 MHz

2002 ◽  
Vol 199 ◽  
pp. 272-273
Author(s):  
K. R. Anantharamaiah ◽  
Namir E. Kassim ◽  
T.J.W. Lazio ◽  
W.M. Goss ◽  
H. Falcke
Keyword(s):  
Galactic Centre ◽  
Large Array ◽  
Very Large Array ◽  
Centre Region

We present a preliminary image of the Galactic Centre region at 74 MHz made using the Very Large Array (VLA)

scholarly journals Radio Images of Planetary Nebulae

1989 ◽  
Vol 131 ◽  
pp. 17-28 ◽  
Author(s):  
Yervant Terzian
Keyword(s):  
Magnetic Field ◽  
Neutral Hydrogen ◽  
Planetary Nebulae ◽  
Aperture Synthesis ◽  
Large Array ◽  
Very Large Array ◽  
Upper Limit ◽  
Neutral Material ◽  
Continuum Radio ◽  
The Continuum

The continuum radio spectra of planetary nebulae are discussed, and the structure of these objects is examined from the observed aperture synthesis brightness distributions determined with the Very Large Array. The use of radio observations in determining distances to planetary nebulae is examined. The detection of atomic neutral hydrogen at λ21 cm associated with planetary nebulae, as well as the associated CO and OH components are discussed. An upper limit, of the nebular magnetic field associated with the neutral material, of 1mG is reported for NGC 6302.

scholarly journals Imaging the water masers toward the H2O-PN IRAS 18061–2505

2012 ◽  
Vol 8 (S287) ◽  
pp. 258-259
Author(s):  
Yolanda Gómez ◽  
Daniel Tafoya ◽  
Olga Suárez ◽  
Jose F. Gómez ◽  
Luis F. Miranda ◽  
...  
Keyword(s):  
Planetary Nebulae ◽  
Central Star ◽  
Large Array ◽  
Maser Emission ◽  
Very Large Array ◽  
Kinematical Model ◽  
Water Masers ◽  
Central Stars ◽  
Water Maser

AbstractIt has been suggested that the presence of disks or tori around the central stars of pre Planetary Nebulae and Planetary Nebulae is related to the collimation of the jet that are frequently observed in these sources. These disks or tori can be traced by the maser emission of some molecules such as water. In this work we present Very Large Array (VLA) observations of the water maser emission at 22 GHz toward the PN IRAS 18061–2505, for which the masers appear located on one side of the central star. For comparison with the observations, we present a simple kinematical model of a disk rotating and expanding around the central star. The model matches qualitatively the observations. However, since the masers appear only on one side of the disk, these results are not conclusive.

scholarly journals High Resolution Maps with the VLA

1983 ◽  
Vol 103 ◽  
pp. 69-78
Author(s):  
R. C. Bignell
Keyword(s):  
New Mexico ◽  
High Resolution ◽  
Radio Astronomy ◽  
Full Time ◽  
Large Array ◽  
Astronomy Observatory ◽  
Very Large Array ◽  
Radio Astronomy Observatory ◽  
Time Operation

The Very Large Array is a radio picture making instrument operated by the National Radio Astronomy Observatory in Socorro, New Mexico. The array, which has been in full time operation for more than 2 1/2 years, operates at four main wavelengths, 1.3, 2.0, 6.0 and 20 cm with achievable resolutions of .05, .08, .25 and 0.8 arc seconds respectively.

scholarly journals Upper Limits on Sub-Arcminute Fluctuations in the CBR

1992 ◽  
Vol 9 ◽  
pp. 333-334
Author(s):  
R. B. Partridge
Keyword(s):  
New Mexico ◽  
Radio Astronomy ◽  
Angular Resolution ◽  
Aperture Synthesis ◽  
Large Array ◽  
Astronomy Observatory ◽  
Very Large Array ◽  
Radio Astronomy Observatory ◽  
Upper Limits

The use of aperture synthesis allows one to search for fluctuations in the CBR on angular scales below 1 arcminute. I report here tentative results of an experiment carried out with E. B. Fomalont, R. Windhorst and J. Lowenthal using the Very Large Array of the National Radio Astronomy Observatory in New Mexico. We used the instrument in its tightest configuration and at a wavelength of 3.6 cm; the corresponding angular resolution was ~10”. We were able to set limits on fluctuations in the CBR on a range of angular scales, 10”-90”, and these are among the most sensitive upper limits on CBR fluctuations yet published.

Sign in / Sign up

Export Citation Format

Share Document