Search

Start Over Subject radio galaxies Validation Level 2
481. VLA 1.4GHz observations of A370 and A2390
ID:
ivo://CDS.VizieR/J/ApJS/202/2
Title:
VLA 1.4GHz observations of A370 and A2390
Short Name:
J/ApJS/202/2
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present 1.4GHz catalogs for the cluster fields A370 and A2390 observed with the Very Large Array. These are two of the deepest radio images of cluster fields ever taken. The A370 image covers an area of 40'x40' with a synthesized beam of ~1.7" and a noise level of ~5.7uJy near the field center. The A2390 image covers an area of 34'x34' with a synthesized beam of ~1.4" and a noise level of ~5.6uJy near the field center. We catalog 200 redshifts for the A370 field. We construct differential number counts for the central regions (radius <16') of both clusters. We find that the faint (S_1.4GHz_<3mJy) counts of A370 are roughly consistent with the highest blank field number counts, while the faint number counts of A2390 are roughly consistent with the lowest blank field number counts. Our analyses indicate that the number counts are primarily from field radio galaxies. We suggest that the disagreement of our number counts can be largely attributed to cosmic variance.
482. VLA Images of Extragalactic Objects
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.
483. VLA 352MHz image of the Bootes field. I.
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.
484. VLA NLS1s southern sample
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.
485. VLA survey of 0016+16, Abell 665, and Abell 2218
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.
486. VLBA 15 and 43GHz obs. of 3C 120
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.
487. VLBA obs. of radio reference frame sources. III.
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.
488. VLBI polarimetry of CJF sources
ID:
ivo://CDS.VizieR/J/ApJ/589/733
Title:
VLBI polarimetry of CJF sources
Short Name:
J/ApJ/589/733
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present Very Long Baseline Array observations and a statistical analysis of 5GHz VLBI polarimetry data from 177 sources in the Caltech-Jodrell Bank Flat-Spectrum (CJF) survey. The CJF survey, a complete, flux density-limited sample of 293 extragalactic radio sources, gives us the unique opportunity to compare a broad range of source properties for quasars, galaxies, and BL Lacertae objects. We focus primarily on jet properties, specifically, the correlation between the jet axis angle and the polarization angle in the core and jet. A strong correlation is found for the electric vector polarization angle in the cores of quasars to be perpendicular to the jet axis. Contrary to previous claims, no correlation is found between the jet polarization angle and the jet axis in either quasars or BL Lac objects. With this large, homogeneous sample we are also able to investigate cosmological issues and active galactic nucleus evolution.
489. VSOP 5 GHz AGN Survey
ID:
ivo://CDS.VizieR/J/PASJ/52/997
Title:
VSOP 5 GHz AGN Survey
Short Name:
J/PASJ/52/997
Date:
21 Oct 2021
Publisher:
CDS
Description:
The VSOP mission is a Japanese-led project to image radio sources with sub-milliarcsec resolution by correlating the signal from the orbiting 8-m telescope, HALCA, with a global array of telescopes. Twenty- five percent of the scientific time of this mission is devoted to a survey of 402 bright, small-diameter extra-galactic radio sources at 5-GHz. The major goals of the VSOP Survey are statistical in nature: to determine the brightness temperature and approximate structure; to provide a source list for use with future space VLBI missions; and to compare radio properties with other data throughout the EM spectrum. This paper describes: the compilation of a complete list of radio sources associated with active galactic nuclei (AGN); the selection of the subsample of sources to be observed with VSOP; the extensive ground resources used for the Survey; the status of the observations as of 2000 July; the data-analysis methods; and several examples of results from the VSOP Survey. More detailed results from the full sample will be given in future papers.
490. VSOP 5 GHz continuum survey
ID:
ivo://CDS.VizieR/J/ApJS/131/95
Title:
VSOP 5 GHz continuum survey
Short Name:
J/ApJS/131/95
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have imaged with milliarcsecond resolution at 5 GHz 374 strong flat-spectrum radio sources north of declination -44{deg} using the VLBA in 1996 June. The source sample was compiled from the source list for the VLBI Space Observatory Programme (VSOP) Survey Program. About 250 of the sources observed with the VLBA had correlated flux densities >=0.3 Jy on the longest VLBA baseline and these sources are currently being observed with VSOP at 5 GHz. This paper presents the results from the VLBA prelaunch observations: the correlated flux density dependence with u-v distance; the contour display of the images; the model fit parameters for each radio component; and improved positions for 62 sources. Comparisons and extensive cross-referencing with other major VLBI surveys are also given.