- ID:
- ivo://CDS.VizieR/J/PASJ/62/525
- Title:
- SiO maser survey off the Galactic Plane
- Short Name:
- J/PASJ/62/525
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A group of Mira variables in the solar neighborhood shows unusual spatial motion in the Galaxy. To study this motion on a much larger scale in the Galaxy, we newly surveyed 134 evolved stars off the Galactic plane by SiO maser lines, obtaining accurate radial velocities of 84 detected stars. Together with the past data of SiO maser sources, we analyzed the radial-velocity data of a large sample of sources distributed in a distance range of about 0.3-6kpc in the first Galactic quadrant. At Galactic longitudes between 20{deg} and 40{deg}, we found a group of stars with large negative radial velocities, which deviate by more than 100km/s from the Galactic rotation. We show that these deviant motions of maser stars are created by periodic gravitational perturbation of the Bulge bar, and that the effect appears most strongly at radii between corotation and outer Lindblad resonances. The resonance effect can explain the displacement of positions from the Galactic plane as well.
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Search Results
- ID:
- ivo://CDS.VizieR/J/PASJ/56/765
- Title:
- SiO maser survey of IRAS sources
- Short Name:
- J/PASJ/56/765
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We surveyed 401 color-selected IRAS sources in the galactic disk in the SiO J=1-0, v=1 and 2 maser lines at 43GHz, resulting in 254 (239 new) detections. The observed sources lie mostly in a strip of the inner galactic disk with boundaries -10{deg}<l<40{deg} and |b|<3{deg}. This survey provides radial velocities of inner-disk stars for which optical measurements cannot be made due to interstellar extinction.
- ID:
- ivo://CDS.VizieR/J/PASJ/64/4
- Title:
- SiO maser survey of nearby red variables
- Short Name:
- J/PASJ/64/4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to study the streaming motions of miras in the Solar neighborhood, we newly surveyed 379 red variables in the SiO maser lines at 42.821 and 43.122GHz with the Nobeyama 45m radio telescope. Accurate radial velocities were obtained for 229 (220 new) detected stars. The sample was selected from optical variables found by new automated surveys: the Northern Sky Variability Survey and the All Sky Automated Survey. The new sample consists of "bluer" objects compared with those observed in the previous SiO surveys. The distances to the objects were estimated using the period-luminosity relation, and they are mostly less than 3kpc from the Sun. The longitude-velocity diagram reveals three prominent groups of stars deviant from circular galactic rotation with a flat rotation curve. In addition to the Hercules group of stars, which was studied before, we found two new deviant groups: one toward the Perseus arm and the other toward the Sagittarius arm. These two groups both exhibit anomalous motions toward the galactic center, which seem to be consistent with the noncircular motions of these spiral arms found in recent VLBI proper-motion measurements for maser gas clumps.
- ID:
- ivo://CDS.VizieR/J/PASJ/55/203
- Title:
- SiO maser survey toward inner Galactic disk
- Short Name:
- J/PASJ/55/203
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of an SiO maser survey for color-selected IRAS sources in the area 40{deg}<l<70{deg} and |b|<10{deg} in the SiO J=1-0, v=1 and 2 transitions (~43GHz). We detected 134 out of 272 observed sources in SiO masers; 127 were new detections. A systematic difference in the detection rates between SiO and OH maser searches was found.
- ID:
- ivo://CDS.VizieR/J/A+A/565/A127
- Title:
- SiO masers v=1,2,3 for 4 AGB
- Short Name:
- J/A+A/565/A127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The v=1 and 2 J=1-0 (43GHz), and v=1 J=2-1 (86GHz) SiO masers are intense in AGB stars and have been mapped using VLBI showing ring-like distributions. Those of the v=1, 2 J=1-0 masers are similar, but the spots are rarely coincident, while the v=1 J=2-1 maser arises from a well separated region farther out. These relative locations can be explained by models including the overlap of two IR lines of SiO and H_2_O. The v=3 J=1-0 line is not directly affected by any line overlap and its spot structure and position, relative to the other lines, will be a good test to the standard pumping models The aims is to gain insight into the properties of the different SiO masers and the general theoretical considerations that can help to understand them. We present single-dish and VLBI simultaneous observations of the v=1, 2, 3 J=1-0 maser transitions of ^28^SiO in several AGB stars. The results are compared with the predictions of radiative models of SiO masers both including and not including the effect of IR line overlap. The spatial distribution of the SiO maser emission in the v=3 J=1-0 transition from AGB stars is systematically composed of a series of spots occupying a ring-like structure (as often found in SiO masers). The overall ring structure is extremely similar to that found in the other 43 GHz transitions, and very different from the structure of the v=1 J=2-1 maser. The positions of the individual spots of the different 43 GHz lines are however very rarely coincident, being in general separated by about 0.3AU (between 1 and 5mas). These results are very difficult to reconcile with standard pumping models, which predict the masers of rotational transitions within a given vibrational state to require very similar excitation conditions (since the levels are placed practically at the same energy from the ground), while the transitions of different vibrational states (which are separated by an energy of 1800K) should appear in different positions. However, models including line overlap tend to predict v=1, 2, 3 J=1-0 population inversion to occur under very similar conditions, while the requirements for v=1 J=2-1 appears clearly different, and are compatible with the observational results.
1566. SIRTF First-Look Survey
- ID:
- ivo://CDS.VizieR/J/AJ/125/2411
- Title:
- SIRTF First-Look Survey
- Short Name:
- J/AJ/125/2411
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The First-Look Survey (FLS) of the Space Infrared Telescope Facility (SIRTF) will cover about 5deg^2^ centered on J2000.0 (17:18+59:30) in order to characterize the extragalactic infrared sky 2 orders of magnitude deeper than the IRAS survey. We expect that most of the FLS far-infrared ({lambda} = 160, 70, and 24 {mu}m) sources will be star-forming galaxies obeying the very tight far-infrared/radio correlation and will be continuum radio sources with flux densities S>~100{mu}Jy at {nu}=1.4GHz. Conversely, radio sources stronger than 100{mu}Jy are usually powered by star-forming galaxies, plus some active galactic nuclei, and most should be detectable by the SIRTF FLS. Thus, a sensitive radio survey can be used to select and identify most of the SIRTF FLS source population before launch. We used the B configuration of the VLA to make an image of the FLS area at {nu}=1.4GHz with {sigma}=~23{mu}Jy/beam rms fluctuations, {theta}=5'' resolution, and {sigma}_{alpha}_=~{sigma}_{delta}_=~0.5'' rms uncertainties in right ascension and declination. The resulting radio image and catalog of 3565 radio components with peak flux densities Sp>=5{sigma}=115{mu}Jy/beam have been released via the Web to expedite follow-up optical identification and spectroscopy.
- ID:
- ivo://CDS.VizieR/J/A+A/598/A76
- Title:
- Six infrared dark clouds multi-wavelength obs.
- Short Name:
- J/A+A/598/A76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Infrared dark clouds (IRDCs) are ubiquitous in the Milky Way, yet they play a crucial role in breeding newly-formed stars. In order to further understand the dynamics, chemistry, and evolution of IRDCs, we carried out multi-wavelength observations towards a small sample. We performed new observations with the IRAM 30m and CSO 10.4m telescopes, with tracers HCO^+^, HCN, N_2_H^+^, C^18^O, DCO^+^, SiO, and DCN towards six IRDCs G031.97+00.07, G033.69-00.01, G034.43+00.24, G035.39-00.33, G038.95-00.47, and G053.11+00.05.
- ID:
- ivo://CDS.VizieR/J/AJ/136/580
- Title:
- Sixth VLBA calibrator survey: VCS6
- Short Name:
- J/AJ/136/580
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents the sixth part of the Very Long Baseline Array (VLBA) Calibrator Survey. It contains the positions and maps of 264 sources of which 169 were not previously observed with very long baseline interferometry. This survey, based on two 24h VLBA observing sessions, was focused on (1) improving positions of 95 sources from previous VLBA Calibrator Surveys that were observed either with very large a priori position errors or were observed not long enough to get reliable positions and (2) observing remaining new flat-spectrum sources with predicted correlated flux density in the range 100-200mJy that were not observed in previous surveys. Source positions were derived from astrometric analysis of group delays determined at the 2.3 and 8.6GHz frequency bands using the Calc/Solve software package. The VCS6 catalog of source positions, plots of correlated flux density versus projected baseline length, contour plots and fits files of naturally weighted CLEAN images, as well as calibrated visibility function files, are available on the Web at http://vlbi.gsfc.nasa.gov/vcs6.
- ID:
- ivo://CDS.VizieR/J/ApJ/766/37
- Title:
- Sizes of MRC radio galaxies and QSOs
- Short Name:
- J/ApJ/766/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the currently popular orientation-based unified scheme, a radio galaxy appears as a quasar when its principal radio-axis happens to be oriented within a certain cone opening angle around the observer's line of sight. Due to geometrical projection, the observed sizes of quasars should therefore appear smaller than those of radio galaxies. We show that this simple, unambiguous prediction of the unified scheme is not borne out by the actually observed angular sizes of radio galaxies and quasars. Except in the original 3CR sample, based on which the unified scheme was proposed, in other much larger samples no statistically significant difference is apparent in the size distributions of radio galaxies and quasars. The population of low-excitation radio galaxies with apparently no hidden quasars inside, which might explain the observed excess number of radio galaxies at low redshifts, cannot account for the absence of any foreshortening of the sizes of quasars at large redshifts. On the other hand, from infrared and X-ray studies, there is evidence of a hidden quasar within a dusty torus in many radio galaxies, at z>0.5. It is difficult to reconcile this with the absence of foreshortening of quasar sizes at even these redshifts, and perhaps one has to allow that the major radio axis may not have anything to do with the optical axis of the torus. Otherwise, to resolve the dichotomy of radio galaxies and quasars, a scheme quite different from the present might be required.
- ID:
- ivo://CDS.VizieR/J/ApJS/74/181
- Title:
- Small-diameter radiosources catalogue
- Short Name:
- J/ApJS/74/181
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A survey of the Galactic plane in the longitude range -20deg=<l<=120deg for Galactic latitudes |b|=<0.8deg has been carried out at 1400MHz using the VLA in the B configuration. We present here a catalog of the 1992 discrete sources detected in this survey which is ~75% complete to a limiting peak flux density of 25mJy for sources smaller than ~20" in diameter, although sources as faint as 8mJy and as large as 90" are also included. The catalog includes for each entry a position accurate to ~<3", peak and integrated flux densities, source extent, and information on counterparts both from earlier radio surveys of the plane (for which a comprehensive bibliography is included) and from the IRAS point source catalog. An extensive analysis of the integrity and completeness of the survey is presented here: in separate publications, we discuss the source content of the survey as derived from statistical analysis of the spatial distribution of the sources and from radio, optical and infrared follow up observations .
