- 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.
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- ID:
- ivo://CDS.VizieR/J/ApJS/124/285
- Title:
- VLA Images of Extragalactic Objects
- Short Name:
- J/ApJS/124/285
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Maps of 212 extragalactic radio sources at 4.9 GHz are shown in Stokes I along with linear polarization vectors. The objects have a declination range of 0 degrees to -35 degrees and were chosen from the Hewitt & Burbidge quasar catalog with a spectral index less than -0.5 and the NVSS survey with a minimum 1.4 GHz flux density greater than 300 mJy. The observations were made with the Very Large Array in its B configuration, and the images have a typical resolution of 2 arcseconds. One hundred ninety-five objects were resolved; 108 of the sources are quasars, and another 51 have been identified as galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/409/115
- Title:
- VLA imaging of IRAS 1 Jy ULIRG sample
- Short Name:
- J/A+A/409/115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents the results of a high resolution radio imaging survey of 83 of the 118 ultraluminous infrared galaxies (ULIRGs) in the IRAS 1Jy ULIRG sample (Kim & Sanders, 1998ApJS..119...41K, Veilleux et al., 2002, Cat. <J/ApJS/143/315>). We have observed these ULIRGs at 15-GHz with the Very Large Array (VLA). We find that ~75% of Seyferts (both type 1 and 2) and LINERs have radio nuclei which are compact at our 150mas resolution. The detection rate of HII nuclei is significantly lower (32%); the detections among these are preferentially HII+LINER/Seyfert composite nuclei. Among ULIRGs with multiple optical or near-IR nuclei our observations detected only one (or no) nucleus; in these the radio detection is typically towards the brightest near-IR nucleus. The compactness of the radio sources, the higher detection rates in AGN-type nuclei than HII nuclei, the preferential detection of nuclei with unresolved point sources in the near-IR, the low soft X-ray to nuclear radio luminosity ratio (arguing against thermal emission powering the radio nuclei), and the lack of correlation between radio power and H{alpha} luminosity, all support an origin of the detected radio nuclei in AGN related activity. This result is especially interesting for LINER ULIRGs for which signatures of AGNs have often been ambiguous in other wavebands. Such a high incidence of AGN would provide, for the first time, a large sample in which to study the interplay between AGN, starbursts, and galaxy mergers.
- ID:
- ivo://CDS.VizieR/J/MNRAS/450/1477
- Title:
- VLA 352MHz image of the Bootes field. I.
- Short Name:
- J/MNRAS/450/1477
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a 324.5MHz image of the NOAO Bootes field that was made using Very Large Array (VLA) P-band observations. The image has a resolution of 5.6"x5.1", a radius of 2.05 degrees and a central noise of ~0.2mJy/beam. Both the resolution and noise of the image are an order of magnitude better than what was previously available at this frequency and will serve as a valuable addition to the already extensive multiwavelength data that are available for this field. The final source catalogue contains 1370 sources and has a median 325 to 1400MHz spectral index of -0.72. Using a radio colour-colour diagram of the unresolved sources in our catalogue, we identify 33 megahertz peaked-spectrum (MPS) sources. Based on the turnover frequency linear size relation for the gigahertz peaked-spectrum (GPS) and compact steep-spectrum (CSS) sources, we expect that the MPS sources that are compact on scales of tens of milliarcseconds should be young radio loud active galactic nuclei at high (z>2) redshifts. Of the 33 MPS sources, we were able to determine redshifts for 24, with an average redshift of 1.3. Given that five of the sources are at z>2, that the four faint sources for which we could not find redshifts are likely at even higher redshifts and that we could only select sources that are compact on a scale of ~5", there is encouraging evidence that the MPS method can be used to search for high-redshift sources.
- ID:
- ivo://CDS.VizieR/J/MNRAS/498/1278
- Title:
- VLA NLS1s southern sample
- Short Name:
- J/MNRAS/498/1278
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of new radio observations carried out with the Karl G. Jansky Very Large Array C-configuration at 5.5GHz for a sample of southern narrow-line Seyfert 1 galaxies (NLS1s). This work increases the number of known radio-detected NLS1s in the southern hemisphere, and confirms that the radio emission of NLS1s is mainly concentrated in a central region at kpc-scale and only a few sources show diffuse emission. In radio-quiet NLS1s, the radio luminosity tends to be higher in steep-spectrum sources and be lower in flat-spectrum sources, which is opposite to radio-loud NLS1s. This may be because the radio emission of steep NLS1s is dominated by misaligned jets, AGN-driven outflows, or star formation superposing on a compact core. Instead the radio emission of flat NLS1s may be produced by a central core which has not yet developed radio jets and outflows. We discover new NLS1s harboring kpc-scale radio jets and confirm that a powerful jet does not require a large-mass black hole to be generated. We also find sources dominated by star formation. These NLS1s could be new candidates in investigating the radio emission of different mechanisms.
- ID:
- ivo://CDS.VizieR/J/ApJS/133/77
- Title:
- VLA radio continuum survey of Seyfert galaxies
- Short Name:
- J/ApJS/133/77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used the Very Large Array (VLA) to conduct a survey for radio continuum emission in the sample of 52 Seyfert nuclei selected from the optical spectroscopic galaxy catalog of Ho, Filippenko, & Sargent (1995, Cat. <J/ApJS/98/477>. This Seyfert sample is the most complete and least biased available, and, as such, it will be useful for a variety of statistical analyses. Here we present the observations, measurements, and an atlas of radio maps. The observations were made at 6 cm in the B array and at 20 cm in the A array, yielding matched angular resolutions of ~1". We detected 44 objects (85%) at 6 cm and 37 objects (71%) at 20 cm above a 3{sigma} threshold of 0.12mJy/beam. The sources have a wide range of radio powers (P~10^19^-10^25^W/Hz), spectral indices ({alpha}^20^_6_~+0.5 to 1), and linear sizes (L~few tens pc - 15kpc). The morphology of the radio emission is predominantly that of a compact core, either unresolved or slightly resolved, occasionally accompanied by elongated, jetlike features. Linearly polarized emission was detected at 6 cm in 12 sources, nine of which were also detected at 20 cm.
- ID:
- ivo://CDS.VizieR/J/AJ/98/1148
- Title:
- VLA survey of 0016+16, Abell 665, and Abell 2218
- Short Name:
- J/AJ/98/1148
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used the VLA to survey the fields of the three clusters of galaxies; 0016+16, Abell 665 (0826+66) and Abell 2218 (1635+66) at 1440 MHz, 4860 MHz, and 14940 MHz (for the brighter sources). The survey was aimed at finding radio sources which might contaminate the Sunyaev-Zel'dovich effect. We have detected 86 sources in these three clusters and examined Palomar sky survey prints for possible optical identifications.
- ID:
- ivo://CDS.VizieR/J/ApJ/808/162
- Title:
- VLBA 15 and 43GHz obs. of 3C 120
- Short Name:
- J/ApJ/808/162
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the analysis of the radio jet evolution of the radio galaxy 3C 120 during a period of prolonged {gamma}-ray activity detected by the Fermi satellite between 2012 December and 2014 October. We find a clear connection between the {gamma}-ray and radio emission, such that every period of {gamma}-ray activity is accompanied by the flaring of the millimeter very long baseline interferometry (VLBI) core and subsequent ejection of a new superluminal component. However, not all ejections of components are associated with {gamma}-ray events detectable by Fermi. Clear {gamma}-ray detections are obtained only when components are moving in a direction closer to our line of sight. This suggests that the observed {gamma}-ray emission depends not only on the interaction of moving components with the millimeter VLBI core, but also on their orientation with respect to the observer. Timing of the {gamma}-ray detections and ejection of superluminal components locate the {gamma}-ray production to within ~0.13pc from the millimeter VLBI core, which was previously estimated to lie about 0.24pc from the central black hole. This corresponds to about twice the estimated extension of the broad line region, limiting the external photon field and therefore suggesting synchrotron self Compton as the most probable mechanism for the production of the {gamma}-ray emission. Alternatively, the interaction of components with the jet sheath can provide the necessary photon field to produced the observed {gamma}-rays by Compton scattering.
- ID:
- ivo://CDS.VizieR/J/A+A/607/A132
- Title:
- VLBA observations of the COSMOS field
- Short Name:
- J/A+A/607/A132
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a project using wide-field Very Long Baseline Interferometry (VLBI) observations at 1.4GHz of 2865 known radio sources in the Cosmic Evolution Survey (COSMOS) field, whose main objective is to determine where Active Galactic Nuclei (AGN) are present. The combination of number of sources, sensitivity, angular resolution and area covered by this project are unprecedented. A catalogue which contains the VLBI detected sources is presented, the main purpose of which is to be used as an AGN catalogue. A catalogue containing complementary multiwavelength information of the VLBI detected sources is also presented.
- ID:
- ivo://CDS.VizieR/J/ApJS/128/17
- Title:
- VLBA obs. of radio reference frame sources. III.
- Short Name:
- J/ApJS/128/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present simultaneous dual-frequency Very Long Baseline Array 2 and 8 GHz observations of 225 of the 560 extragalactic sources for which positions were reported by Johnston and coworkers and which are now part of the International Celestial Reference Frame. These observations represent the third and final in a series of observations intended to obtain single-epoch images of the entire set of sources presented by Johnston and coworkers (1995, Cat. <J/AJ/110/880>) and, together with previously reported observations, bring the total number of sources observed to 389. As with previous papers in this series, we use these data to quantify the magnitude of the expected effect of intrinsic source structure on astrometric bandwidth synthesis Very Long Baseline Interferometry observations and to calculate a source "structure index" for the observed sources. The structure index can be used as an estimate of the astrometric quality of the sources. Based on this indicator, correlations between the observed radio structure and the astrometric position accuracy and stability of the sources have been found. These correlations indicate that the more extended sources have larger position uncertainties and are less positionally stable than the more compact sources.
