- ID:
- ivo://CDS.VizieR/J/ApJ/582/756
- Title:
- Velocities of HII regions
- Short Name:
- J/ApJ/582/756
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Kinematic distance determinations in the inner Galaxy are hampered by the near-far kinematic distance ambiguity. Here we resolve the ambiguity for 49 HII region complexes with known recombination-line velocities in the first Galactic quadrant. We measured the 21cm HI absorption spectrum toward each source with the Very Large Array in the C array. The maximum velocity of HI absorption was used to discriminate between the near and far kinematic distances. The number ratio of far to near sources, ~3, can be entirely explained as a geometrical effect. The kinematic distances that we derive are compared with previous determinations for the same sources. Although our distance determinations are largely in agreement with previous measurements, there are 22 discrepancies that we discuss. Using our distance determinations, we create a face-on Galactic map of the HII region complexes and compare it with a kinematically derived profile of the distribution of CO-traced molecular hydrogen. The HII region complexes delineate the large-scale features seen in the molecular gas. The 5kpc molecular ring and the Sagittarius spiral arm are clearly evident, and a few HII region complexes lie in the Perseus arm.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/other/ChJAA/3.49
- Title:
- Velocity and distance of methanol maser sources
- Short Name:
- J/other/ChJAA/3.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a statistical analysis of 482 6.7GHz methanol maser sources from the available literature, on their maser emission and the characteristics of their associated infrared sources. On the color-color diagram, more than 70% of the objects fall within a very small region (0.57<=[25-12]<=1.30 and 1.30<=[60-12]<=2.50). This suggests that 6.7GHz methanol maser emission occurs only within a very short evolutionary phase during the earliest stage of star formation. The velocity ranges of the masers belong to two main groups: one from 1 to 10km/s, and one from about 11 to 20km/s. These velocity ranges indicate that the masers are probably associated with both disks and outflows. The correlations between the maser and infrared flux densities, and between the maser and infrared luminosities, suggest that far-infrared radiation is a possible pumping mechanism for the masers which most probably originate from some outer molecular envelopes or disks.
- ID:
- ivo://CDS.VizieR/J/ApJ/585/647
- Title:
- Velocity dispersion in AGN
- Short Name:
- J/ApJ/585/647
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It has been proposed that the width of the narrow [O III] {lambda}5007 emission line can be used as a surrogate for the stellar velocity dispersion in active galaxies. This proposition is tested using the Sloan Digital Sky Survey (SDSS) Early Data Release (EDR) spectra of 107 low-redshift radio-quiet QSOs and Seyfert 1 galaxies by investigating the correlation between black hole mass, as determined from H{beta} FWHM and optical luminosity, and [O III] FWHM. The correlation is real, but the scatter is large. Without additional information or selection criteria, the [O III] width can predict the black hole mass to a factor of 5.
- ID:
- ivo://CDS.VizieR/J/ApJ/622/187
- Title:
- Velocity of eight RASSCALS galaxy groups
- Short Name:
- J/ApJ/622/187
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the distribution of gas pressure and entropy in eight groups of galaxies belonging to the ROSAT All-Sky Survey/Center for Astrophysics Loose Systems (RASSCALS, Cat. <J/ApJ/534/114>). We use archival and proprietary XMM-Newton observations, supplementing the X-ray data with redshifts derived from the literature; we also list 125 new redshifts measured with the Gemini North telescope.
- ID:
- ivo://CDS.VizieR/J/AJ/133/2487
- Title:
- VERA 22GHz Fringe Search Survey
- Short Name:
- J/AJ/133/2487
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents results of a survey search for bright compact radio sources at 22GHz with the VERA radio interferometer. Each source from a list of 2494 objects was observed in one scan for 2 minutes. The purpose of this survey was to find compact extragalactic sources bright enough at 22GHz to be useful as phase calibrators. Observed sources were either (1) within 6{deg} of the Galactic plane, or (2) within 11{deg} of the Galactic center, or (3) within 2{deg} of known water masers. Among the observed sources, 549 were detected, including 180 extragalactic objects that were not previously observed with the very long baseline interferometry technique. Estimates of the correlated flux densities of the detected sources are presented. It was found that the probability of detecting a 200mJy source with 120s of integration time is 60%.
- ID:
- ivo://CDS.VizieR/J/A+A/267/515
- Title:
- Very cold C-rich circumstellar envelopes
- Short Name:
- J/A+A/267/515
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The paper develops a method for identification of very cold C-rich circumstellar envelopes (CSEs) in IR regions colder than region VII (i.e., larger value of IRAS flux ratio S25/S12), by reviewing the different criteria and by identifying C-rich CSEs in a sample of 228 bright IRAS sources. By using the results of OH surveys and catalogs together with the results of additional HCN/CO millimeter observations performed on critical classes of objects, a C/O classification is proposed for 94 percent of the sources with a good probability. It is shown that the low-resolution spectra by themselves are a reasonable and easy way to identify C-rich late AGB CSEs. For post-AGB object with cold CSEs, HCN and OH observations or visible/near IR spectroscopy are necessary.
- ID:
- ivo://CDS.VizieR/J/ApJS/146/267
- Title:
- Very rich Abell clusters radio analysis
- Short Name:
- J/ApJS/146/267
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Radio observations were used to detect the "active" galaxy population within rich clusters of galaxies in a nonbiased manner that is not plagued by dust extinction or the K-correction. We present wide-field radio, optical (imaging and spectroscopy), and ROSAT All-Sky Survey (RASS, Cat. <IX/10>) X-ray data for a sample of 30 very rich Abell (R>=2) cluster with z<=0.25. The VLA radio data samples the ultrafaint radio (L(1.4GHz)>=2x10^22^W/Hz) galaxy population within these extremely rich clusters for galaxies with RMAG<=-21. This is the largest sample of low-luminosity 20 cm radio galaxies within rich Abell clusters collected to date.
- ID:
- ivo://CDS.VizieR/J/MNRAS/360/340
- Title:
- Very Small Array. Flux density at 33GHz
- Short Name:
- J/MNRAS/360/340
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe the source subtraction strategy and observations for the extended Very Small Array (VSA), a cosmic microwave background interferometer operating at 33GHz. A total of 453 sources were monitored at 33GHz using a dedicated source subtraction baseline. 131 sources brighter than 20mJy were directly subtracted from the VSA visibility data. Some characteristics of the subtracted sources, such as spectra and variability, are discussed. The 33GHz source counts are estimated from a sample selected at 15GHz. The selection of VSA fields in order to avoid bright sources introduces a bias into the observed counts. This bias is corrected and the resulting source count is estimated to be complete in the flux-density range 20114mJy. The 33GHz source counts are used to calculate a correction to the VSA power spectrum for sources below the subtraction limit.
- ID:
- ivo://CDS.VizieR/J/MNRAS/341/1066
- Title:
- Very Small Array. II. CMB at 34GHz
- Short Name:
- J/MNRAS/341/1066
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have observed the cosmic microwave background (CMB) temperature fluctuations in eight fields covering three separated areas of sky with the Very Small Array at 34GHz. A total area of 101 square degrees has been imaged, with sensitivity on angular scales of 3.6{deg}-0.4{deg} (equivalent to angular multipoles l=150-900).
- ID:
- ivo://mast.stsci/siap/al218
- Title:
- VLA-A Array AL218 Texas Survey Source Snapshots (AL218)
- Short Name:
- VLA.AL218
- Date:
- 23 Jul 2020 19:30:09
- Publisher:
- Space Telescope Science Institute Archive
- Description:
- The VLA-A Texas Survey consists of a sample of objects extracted from the earlier Texas Interferometer 365 MHz Survey of radio sources covering a strip of sky from approximately -35.5 degrees declination to +71.5 degrees declination, and complete to flux densities of 0.25 Jy, with positional accuracies of ~1 arcsecond in RA and DEC. The sample is a subset of 71 sources drawn from the area of one optical Schmidt sky survey plate (covering ~6.5x6.5 degrees), Region S861, centered at approximately RA=190.640822109, DEC=-0.273834224277 (J2000), from the UK Schmidt SRC-J Survey. The Region S861 was initially chosen because it represented the combination of the deepest UK Schmidt plate material (the best optical survey material available at the time of the sample definition in 1989) and the highest galactic latitude, thereby emphasizing the extragalactic nature of the survey and also maximizing the likelihood of having more optical detections. Much more recently, the area of this plate has been covered by a number of important sky surveys including 2MASS, NRAO VLA FIRST, and the Sloan Digital Sky Survey (SDSS) which is now public. In particular, the availability of the Sloan Survey data provides 5-band ugriz color information at optical wavelengths, to depth of g,r=22.2.
