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17041. VLA 1.4GHz observations of GOODS-North field
ID:
ivo://CDS.VizieR/J/ApJS/188/178
Title:
VLA 1.4GHz observations of GOODS-North field
Short Name:
J/ApJS/188/178
Date:
21 Oct 2021
Publisher:
CDS
Description:
We describe deep, new, wide-field radio continuum observations of the Great Observatories Origins Deep Survey-North field. The resulting map has a synthesized beam size of ~1.7" and an rms noise level of ~3.9uJy/beam near its center and ~8uJy/beam at 15' from phase center. We have cataloged 1230 discrete radio emitters, within a 40'x40' region, above a 5{sigma} detection threshold of ~20uJy at the field center. New techniques, pioneered by Owen & Morrison, have enabled us to achieve a dynamic range of 6800:1 in a field that has significantly strong confusing sources. We compare the 1.4GHz (20cm) source counts with those from other published radio surveys. Our differential counts are nearly Euclidean below 100uJy with a median source diameter of ~1.2". This adds to the evidence presented by Owen & Morrison that the natural confusion limit may lie near 1uJy. If the Euclidean slope of the counts continues down to the natural confusion limit as an extrapolation of our logN-logS, this indicates that the cutoff must be fairly sharp below 1uJy else the cosmic microwave background temperature would increase above 2.7K at 1.4GHz.
17042. VLA 6-GHz Observations of Low-Redshift SDSS QSOs
ID:
ivo://nasa.heasarc/lowzvlqvla
Title:
VLA 6-GHz Observations of Low-Redshift SDSS QSOs
Short Name:
LOWZVLQVLA
Date:
01 Nov 2024
Publisher:
NASA/GSFC HEASARC
Description:
This table contains results from 6-GHz Jansky Very Large Array (JVLA) observations covering a volume-limited sample of 178 low-redshift (0.2 < z <0.3) optically selected quasi-stellar objects (QSOs). These 176 radio detections fall into two clear categories: (1) about 20% are radio-loud QSOs (RLQs) with spectral luminosities of L<sub>6</sub> >~ 10<sup>23.2</sup> W/Hz that are primarily generated in the active galactic nucleus (AGN) responsible for the excess optical luminosity that defines a bona fide QSO; and (2) the remaining 80% that are radio-quiet QSOs (RQQs) that have 10<sup>21</sup> <~ L<sub>6</sub> <~ 10<sup>23.2</sup> W/Hz and radio sizes <~ 10 kpc, and the authors suggest that the bulk of their radio emission is powered by star formation in their host galaxies. "Radio-silent" QSOs (L_6_<~ 10<sup>21</sup> W/Hz) are rare, so most RQQ host galaxies form stars faster than the Milky Way; they are not "red and dead" ellipticals. Earlier radio observations did not have the luminosity sensitivity of L<sub>6</sub> <~ 10<sup>21</sup> W/Hz that is needed to distinguish between such RLQs and RQQs. Strong, generally double-sided radio emission spanning >> 10 kpc was found to be associated with 13 of the 18 RLQ cores with peak flux densities of S<sub>p</sub> > 5 mJy/beam (log(L) >~ 24). The radio luminosity function of optically selected QSOs and the extended radio emission associated with RLQs are both inconsistent with simple "unified" models that invoke relativistic beaming from randomly oriented QSOs to explain the difference between RLQs and RQQs. Some intrinsic property of the AGN or their host galaxies must also determine whether or not a QSO appears radio-loud. The authors have reprocessed the VLA observations of a sample of SDSS QSOs discussed in Kimball et al. (2011, ApJ, 739, L29). These were obtained using the VLA C configuration with a central frequency of 6 GHz and a bandwidth of 2 GHz in each of the two circular polarizations: with natural weighting the synthesized beam width was 3.5 arcseconds FWHM. The authors generated a catalog of radio sources associated with each QSO. They detected radio emission at 6 GHz from all but two of the 178 color-selected SDSS QSOs contained in this volume-limited sample of QSOs more luminous than M<sub>i</sub> = -23 and with redshifts 0.2 < z < 0.3. All calculations in the reference paper assume a flat LambdaCDM cosmology with H<sub>0</sub> = 70 km s<sup>-1</sup> Mpc<sup>-1</sup> and Omega<sub>Lambda</sub> = 0.7. Spectral luminosities are specified by their source-frame frequencies, flux densities are specified in the observer's frame, and a mean spectral index of alpha = d(log S)/d(log nu) = -0.7 is used to make frequency conversions This table was created by the HEASARC in April 2017 based upon the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/831/168">CDS Catalog J/ApJ/831/168</a> file table1.dat. This is a service provided by NASA HEASARC .
17043. VLA 9GHz obs. of HII region candidates
ID:
ivo://CDS.VizieR/J/ApJS/253/23
Title:
VLA 9GHz obs. of HII region candidates
Short Name:
J/ApJS/253/23
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Milky Way contains thousands of HII region candidates identified by their characteristic mid-infrared morphology, but lacking detections of ionized gas tracers such as radio continuum or radio recombination line emission. These targets thus remain unconfirmed as HII regions. With only ~2500 confirmed HII regions in the Milky Way, Galactic surveys are deficient by several thousand nebulae when compared to external galaxies with similar star formation rates. Using sensitive 9 GHz radio continuum observations with the Karl G. Jansky Very Large Array, we explore a sample of HII region candidates in order to set observational limits on the actual total population of Galactic HII regions. We target all infrared-identified "radio-quiet" sources from the Wide-field Infrared Survey Explorer Catalog of Galactic HII regions between 245{deg}>=l>=90{deg} with infrared diameters less than 80". We detect radio continuum emission from 50% of the targeted HII region candidates, providing strong evidence that most of the radio-quiet candidates are bona fide HII regions. We measure the peak and integrated radio flux densities and compare the inferred Lyman continuum fluxes using models of OB stars. We conclude that stars of approximately spectral type B2 and earlier are able to create HII regions with similar infrared and radio continuum morphologies as the more luminous HII regions created by O stars. From our 50% detection rate of "radio-quiet" sources, we set a lower limit of ~7000 for the HII region population of the Galaxy. Thus the vast majority of the Milky Way's HII regions remain to be discovered.
17044. VLA 33GHz obs. of star-forming regions
ID:
ivo://CDS.VizieR/J/ApJS/234/24
Title:
VLA 33GHz obs. of star-forming regions
Short Name:
J/ApJS/234/24
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present 33GHz imaging for 112 pointings toward galaxy nuclei and extranuclear star-forming regions at ~2" resolution using the Karl G. Jansky Very Large Array (VLA) as part of the Star Formation in Radio Survey. A comparison with 33GHz Robert C. Byrd Green Bank Telescope single-dish observations indicates that the interferometric VLA observations recover 78%+/-4% of the total flux density over 25" regions (~kpc scales) among all fields. On these scales, the emission being resolved out is most likely diffuse non-thermal synchrotron emission. Consequently, on the ~30-300pc scales sampled by our VLA observations, the bulk of the 33GHz emission is recovered and primarily powered by free-free emission from discrete HII regions, making it an excellent tracer of massive star formation. Of the 225 discrete regions used for aperture photometry, 162 are extranuclear (i.e., having galactocentric radii rG>=250pc) and detected at >3{sigma} significance at 33GHz and in H{alpha}. Assuming a typical 33GHz thermal fraction of 90%, the ratio of optically-thin 33GHz to uncorrected H{alpha} star formation rates indicates a median extinction value on ~30-300pc scales of A_H{alpha}_~1.26+/-0.09mag, with an associated median absolute deviation of 0.87mag. We find that 10% of these sources are "highly embedded" (i.e., A_H{alpha}_>~3.3mag), suggesting that on average, HII regions remain embedded for <~1Myr. Finally, we find the median 33GHz continuum-to-H{alpha} line flux ratio to be statistically larger within rG<250pc relative to the outer disk regions by a factor of 1.82+/-0.39, while the ratio of 33GHz to 24{mu}m flux densities is lower by a factor of 0.45+/-0.08, which may suggest increased extinction in the central regions.
17045. VLA 3GHz radio source catalog in the Lockman Hole
ID:
ivo://CDS.VizieR/J/ApJ/856/67
Title:
VLA 3GHz radio source catalog in the Lockman Hole
Short Name:
J/ApJ/856/67
Date:
21 Oct 2021
Publisher:
CDS
Description:
We made two new sensitive (rms noise {sigma}_n_~1{mu}Jy/beam) high-resolution ({theta}=3.0" and {theta}=0.66" FWHM) S-band (2<{nu}<4GHz) images covering a single JVLA primary beam (FWHM~14') centered on RAJ2000=10:46,DEJ2000=+59:01 in the Lockman Hole. These images yielded a catalog of 792 radio sources, 97.7+/-0.8% of which have infrared counterparts stronger than S~2{mu}Jy at {lambda}=4.5{mu}m. About 91% of the radio sources found in our previously published, comparably sensitive low-resolution ({theta}=8" FWHM) image covering the same area were also detected at 0.66" resolution, so most radio sources with S(3GHz)>~5{mu}Jy have angular structure {phi}<~0.66". The ratios of peak brightness in the 0.66" and 3" images have a distribution indicating that most {mu}Jy radio sources are quite compact, with a median Gaussian angular diameter <{phi}>=0.3"+/-0.1" FWHM and an rms scatter {sigma}_{phi}_<~0.3" of individual sizes. Most of our {mu}Jy radio sources obey the tight far-infrared/radio correlation, indicating that they are powered by star formation. The median effective angular radius enclosing half the light emitted by an exponential disk is <{rho}_e_>~<{phi}>/2.43~0.12", so the median effective radius of star-forming galaxies at redshifts z~1 is <r_e_>~1.0kpc.
17046. VLA 1.4GHz survey of E-CDF-S
ID:
ivo://CDS.VizieR/J/ApJS/179/114
Title:
VLA 1.4GHz survey of E-CDF-S
Short Name:
J/ApJS/179/114
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have observed the Extended Chandra Deep Field-South (E-CDF-S) using a mosaic of six deep Very Large Array (VLA) pointings at 1.4GHz. In this paper, we present the survey strategy, description of the observations, and the first data release. The observations were performed during June through September of 2007 and included from 15 to 17 "classic" VLA antennas and 6 to 11 that had been retrofitted for the Expanded VLA (EVLA). The first data release consists of a 34.1'x34.1' image and the attendant source catalog. The image achieves an rms sensitivity of 6.4{mu}Jy per 2.8"x1.6" beam in its deepest regions, with a typical sensitivity of 8uJy. The catalog is conservative in that it only lists sources with peak flux densities greater than seven times the local rms noise, yet it still contains 464 sources. Nineteen of these are complex sources consisting of multiple components. Cross matching of the catalog to prior surveys of the E-CDF-S confirms the linearity of the flux density calibration, albeit with a slight possible offset (a few percent) in scale. Improvements to the data reduction and source catalog are ongoing, and we intend to produce a second data release in 2009 January.
17047. VLA 1.4GHz survey of ECDF-S (DR2)
ID:
ivo://CDS.VizieR/J/ApJS/205/13
Title:
VLA 1.4GHz survey of ECDF-S (DR2)
Short Name:
J/ApJS/205/13
Date:
21 Oct 2021
Publisher:
CDS
Description:
Deep radio observations at 1.4GHz for the Extended Chandra Deep Field South were performed in 2007 June through September and presented in a first data release. The survey was made using six separate pointings of the Very Large Array with over 40hr of observation per pointing. In the current paper, we improve on the data reduction to produce a second data release (DR2) mosaic image. This DR2 image covers an area of about a third of a square degree, reaches a best rms sensitivity of 6uJy, and has a typical sensitivity of 7.4uJy per 2.8" by 1.6" beam. We also present a more comprehensive catalog, including sources down to peak flux densities of five or more times the local rms noise along with information on source sizes and relevant pointing data. We discuss in some detail the consideration of whether sources are resolved under the complication of a radio image created as a mosaic of separate pointings each suffering some degree of bandwidth smearing, and the accurate evaluation of the flux densities of such sources. Finally, the radio morphologies and optical/near-IR counterpart identifications are used to identify 17 likely multiple-component sources and arrive at a catalog of 883 radio sources, which is roughly double the number of sources contained in the first data release.
17048. VLA 22GHz water masers obs. in NGC6334I-MM1
ID:
ivo://CDS.VizieR/J/ApJ/866/87
Title:
VLA 22GHz water masers obs. in NGC6334I-MM1
Short Name:
J/ApJ/866/87
Date:
21 Oct 2021
Publisher:
CDS
Description:
We compare multi-epoch sub-arcsecond Very Large Array imaging of the 22GHz water masers toward the massive protocluster NGC 6334I observed before and after the recent outburst of MM1B in (sub)millimeter continuum. Since the outburst, the water maser emission toward MM1 has substantially weakened. Simultaneously, the strong water masers associated with the synchrotron continuum point source CM2 have flared by a mean factor of 6.5 (to 4.2kJy) with highly blueshifted features (up to 70km/s from the LSR) becoming more prominent. The strongest flaring water masers reside 3000au north of MM1B and form a remarkable bow shock pattern whose vertex coincides with CM2 and tail points back to MM1B. Excited OH masers trace a secondary bow shock located ~120au downstream. Atacama Large Millimeter Array images of CS (6-5) reveal a highly collimated north-south structure encompassing the flaring masers to the north and the nonflaring masers to the south seen in projection toward the MM3-UCHII region. Proper motions of the southern water masers over 5.3 years indicate a bulk projected motion of 117km/s southward from MM1B with a dynamical time of 170 years. We conclude that CM2, the water masers, and many of the excited OH masers trace the interaction of the high-velocity bipolar outflow from MM1B with ambient molecular gas. The previously excavated outflow cavity has apparently allowed the radiative energy of the current outburst to propagate freely until terminating at the northern bow shock where it strengthened the masers. Additionally, water masers have been detected toward MM7 for the first time, and a highly collimated CS (6-5) outflow has been detected toward MM4.
17049. VLA GOODS-North Field 1.4-GHz Source Catalog
ID:
ivo://nasa.heasarc/vlagoodsn
Title:
VLA GOODS-North Field 1.4-GHz Source Catalog
Short Name:
VLAGOODSN
Date:
01 Nov 2024
Publisher:
NASA/GSFC HEASARC
Description:
This table contains results from deep, new, wide-field radio continuum observations of the Great Observatories Origins Deep Survey-North (GOODS-North) field. (The GOODS-North field covers ~160 arcmin&lt;sup&gt;2&lt;/sup&gt; centered on the Hubble Deep Field North (Williams et al. 1996, AJ, 112, 1335) and is unrivaled in terms of its ancillary data sets, which include extremely deep Chandra, Hubble Space Telescope (HST), and Spitzer observations, deep UBVRIJHK ground-based imaging and ~3500 spectroscopic redshifts from 8 to 10 m telescopes). The resulting 1.4-GHz map has a synthesized beam size of ~1.7&quot; and an rms noise level of ~3.9 microJansky per beam (&micro;Jy/beam) near its center and ~8 &micro;Jy/beam at 15 arcminutes from phase center. The authors have cataloged 1230 discrete radio emitters, within a 40&#39; x 40&#39; region, above a 5-sigma detection threshold of ~20 uJy at the field center. New techniques, pioneered by Owen &amp; Morrison (2008, AJ, 136, 1889), have enabled the authors to achieve a dynamic range of 6800:1 in a field that has significantly strong confusing sources. The authors compare the 1.4-GHz (20-cm) source counts with those from other published radio surveys. Their differential counts are nearly Euclidean below 100 uJy with a median source diameter of ~1.2&quot;. This adds to the evidence presented by Owen &amp; Morrison that the natural confusion limit may lie near 1 uJy. If the Euclidean slope of the counts continues down to the natural confusion limit as an extrapolation of their log N-log S, this indicates that the cutoff must be fairly sharp below 1 uJy, else the cosmic microwave background temperature would increase above 2.7K at 1.4GHz. A useful combined total of 165 hours of NRAOS&#39;s Very Large Array (VLA) A-configuration 1.4-GHz observations were obtained between 2005 February and 2006 February, all done at night so as to avoid solar interference, for a region centered at RA and Dec of 12:36:49.4, +62:12:58 (J2000). (See Table 1 of the reference paper for the VLA observing log) This table was created by the HEASARC in September 2013 based on &lt;a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJS/188/178"&gt;CDS Catalog J/ApJS/188/178&lt;/a&gt; file table2.dat This is a service provided by NASA HEASARC .
17050. VLA Goulds Belt Survey Ophiuchus Complex Source Catalog
ID:
ivo://nasa.heasarc/vlagbsoph
Title:
VLA Goulds Belt Survey Ophiuchus Complex Source Catalog
Short Name:
VLAGBSOPH
Date:
01 Nov 2024
Publisher:
NASA/GSFC HEASARC
Description:
This table contains results from large-scale (~2000 arcmin&lt;sup&gt;2&lt;/sup&gt;), deep (~20 &micro;Jy), high-resolution (~1&quot;) radio observations of the Ophiuchus star-forming complex obtained with the Karl G. Jansky Very Large Array (JVLA) at wavelengths of 4 and 6 cm (frequencies of 7.5 and 4.5 GHz). In total, 189 sources were detected, 56 of them associated with known young stellar objects (YSOs), and 4 with known extragalactic objects; the other 129 remain unclassified, but most of them are most probably background quasars. The vast majority of the young stars detected at radio wavelengths have spectral types K or M, although four objects of A/F/B types and two brown dwarf candidates are also detected. At least half of these young stars are non-thermal (gyrosynchrotron) sources, with active coronae characterized by high levels of variability, negative spectral indices, and (in some cases) significant circular polarization. As expected, there is a clear tendency for the fraction of non-thermal sources to increase from the younger (Class 0/I or flat spectrum) to the more evolved (Class III or weak-line T Tauri) stars. The young stars detected both in X-rays and at radio wavelengths broadly follow a Gudel-Benz relation, but with a different normalization than the most radio-active types of stars. Finally, the authors detected a ~70 mJy compact extragalactic source near the center of the Ophiuchus core, which should be used as gain calibrator for any future radio observations of this region. The observations were obtained with the JVLA of the National Radio Astronomy Observatory (NRAO). Two frequency sub-bands, each 1-GHz wide, and centered at 4.5 and 7.5 GHz, respectively, were recorded simultaneously. The observations were obtained on three different epochs (2011 February 17/19, April 3/4, and May 4/6) typically separated from one another by a month. The angular resolution of the observations is of the order of 1 arcsecond. To identify sources in their observations, the authors used the images corresponding to the concatenation of the three epochs, which provided the highest sensitivity. The criteria used to consider a detection as firm were: (1) sources with reported counterparts and a flux larger than four times the rms noise of the area, or (2) sources with a flux larger than five times the rms noise of the area and without reported counterparts. The authors searched the literature for previous radio detections, and for counterparts at X-ray, optical, near-infrared, and mid-infrared wavelengths. The search was done in SIMBAD, and accessed all the major catalogs (listed explicitly in the footnote of Table 3 in the reference paper). Note that the Spitzer c2d catalog includes cross-references to other major catalogs which were taken into account in their counterpart search. The authors considered a radio source associated with a counterpart at another wavelengths if the separation between the two was below the combined uncertainties of the two data sets. This was about 1.5 arcseconds for the optical and infrared catalogs, but could be significantly larger for some of the radio catalogs (for instance, the NVSS has a positional uncertainty of about 5 arcseconds). The authors found that only 76 of the sources detected here had previously been reported at radio wavelengths (matches are listed in the radio_name parameter in such cases), while the other 113 are new radio detections. On the other hand, they found a total of 100 counterparts at other wavelengths. Note that there are a significant number of sources that were previously known at radio wavelengths and have known counterparts at other frequencies. As a consequence, the number of sources that were previously known (at any frequency) is 134, while 55 of the sources in this sample are reported here for the first time. The authors argue that most of these 55 objects are likely background sources. They note, however, that 18 of the 129 unclassified objects (55 identified here for the first time and 74 previously known at radio wavelengths) are compact, have a positive spectral index, or exhibit high variability. Since these latter two properties are not expected of quasars (which are certainly variable, but usually not strongly on such short timescale), but would be natural characteristics of young stars, the authors argue that a small population of YSOs might be present among the unclassified sources. This population could account for, at most, 15% of the unclassified sources, and possibly significantly less. This table was created by the HEASARC in July 2015 based on electronic versions of Tables 1, 3 and 5 from the reference paper, which were obtained from the CDS (Catalog J/ApJ/775/63 files table1.dat, table3.dat and table5.dat). This is a service provided by NASA HEASARC .

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