- ID:
- ivo://CDS.VizieR/J/MNRAS/381/211
- Title:
- Radio galaxies in the 2SLAQ LRG Survey
- Short Name:
- J/MNRAS/381/211
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have combined optical data from the 2dF-SDSS (Sloan Digital Sky Survey) LRG (Luminous Red Galaxy) and QSO (quasi-stellar object) (2SLAQ) redshift survey with radio measurements from the 1.4GHz VLA (Very Large Array) FIRST (Faint Images of the Radio Sky at Twenty-cm) and NVSS (NRAO VLA Sky Survey) surveys to identify a volume-limited sample of 391 radio galaxies at redshift 0.4<z<0.7. By determining an accurate radio luminosity function for luminous early-type galaxies in this redshift range, we can investigate the cosmic evolution of the radio-galaxy population over a wide range in radio luminosity.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/362/9
- Title:
- Radio-loud AGN in SDSS
- Short Name:
- J/MNRAS/362/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A sample of 2712 radio-luminous galaxies is defined from the second data release of the Sloan Digital Sky Survey (SDSS) by cross-comparing the main spectroscopic galaxy sample with two radio surveys: the National Radio Astronomy Observatories (NRAO) Very Large Array (VLA) Sky Survey (NVSS, <VIII/65>) and the Faint Images of the Radio Sky at Twenty centimeters (FIRST, <VIII/71>) survey. The comparison is carried out in a multistage process and makes optimal use of both radio surveys by exploiting the sensitivity of the NVSS to extended and multicomponent radio sources in addition to the high angular resolution of the FIRST images. A radio source sample with 95 per cent completeness and 98.9% reliability is achieved, far better than would be possible for this sample if only one of the surveys was used. The radio source sample is then divided into two classes: radio-loud active galactic nuclei (AGN) and galaxies in which the radio emission is dominated by star formation. The division is based on the location of a galaxy in the plane of 4000{AA} break strength versus radio luminosity per unit stellar mass and provides a sample of 2215 radio-loud AGN and 497 star-forming galaxies brighter than 5mJy at 1.4GHz. A full catalogue of positions and radio properties is provided for these sources.
- ID:
- ivo://CDS.VizieR/J/MNRAS/460/3202
- Title:
- Radio-loud AGN with relativistic jets
- Short Name:
- J/MNRAS/460/3202
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep near-infrared (NIR) images of a sample of 19 intermediate-redshift (0.3<z<1.0) radio-loud active galactic nuclei (AGN) with powerful relativistic jets (L_1.4GHz_>10^27^W/Hz), previously classified as flat-spectrum radio quasars. We also compile host galaxy and nuclear magnitudes for blazars from literature. The combined sample (this work and compilation) contains 100 radio-loud AGN with host galaxy detections and a broad range of radio luminosities L_1.4GHz_~10^23.7^-10^28.3^W/Hz, allowing us to divide our sample into high-luminosity blazars (HLBs) and low-luminosity blazars (LLBs). The host galaxies of our sample are bright and seem to follow the {mu}_e_-Reff relation for ellipticals and bulges. The two populations of blazars show different behaviours in the M_K,nuclear_-M_K,bulge_ plane, where a statistically significant correlation is observed for HLBs. Although it may be affected by selection effects, this correlation suggests a close coupling between the accretion mode of the central supermassive black hole and its host galaxy, which could be interpreted in terms of AGN feedback. Our findings are consistent with semi-analytical models where low-luminosity AGN emit the bulk of their energy in the form of radio jets, producing a strong feedback mechanism, and high-luminosity AGN are affected by galaxy mergers and interactions, which provide a common supply of cold gas to feed both nuclear activity and star formation episodes.
- ID:
- ivo://CDS.VizieR/J/MNRAS/461/2346
- Title:
- Radio-loud and radio-quiet quasars sample
- Short Name:
- J/MNRAS/461/2346
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We compare covering factors of circumnuclear dusty obscurers in radio-loud and radio-quiet quasars. The radio-loud quasars are represented by a sample of FR II quasars obtained by cross-matching a catalog of the FR II radio sources selected by van Velzen et al. with the SDSS DR7 catalog of quasars. Covering factors of FR II quasars are compared with covering factors of the radio-quiet quasars matched with them in redshift, black hole mass, and Eddington-ratio. We found that covering factors, proxied by the infrared-to-bolometric luminosity ratio, are on average slightly smaller in FR II quasars than in radio-quiet quasars, however, this difference is statistically significant only for the highest Eddington ratios. For both samples, no statistically significant dependence of a median covering factor on Eddington ratio, black hole mass, nor redshift can be claimed.
- ID:
- ivo://CDS.VizieR/J/MNRAS/348/857
- Title:
- Radio-loud QSOs at z~4
- Short Name:
- J/MNRAS/348/857
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We obtained spectra of 60 red, star-like objects (m_E_<18.8) identified with FIRST radio sources, S_1.4GHz_>1mJy. Eight are quasi-stellar objects (QSOs) with redshift z>3.6. Combined with our earlier pilot search, our sample of 121 candidates yields a total of 18 z>3.6 QSOs (10 of these with z>4.0). 8 per cent of candidates with S_1.4GHz_<10mJy and 37 per cent of candidates with S_1.4GHz_>10mJy are QSOs with z>3.6. The surface density of m_E_<18.8, S_1.4GHz_>1mJy, z>4 QSOs is 0.003deg^-2^. This is currently the only well-defined sample of radio-loud QSOs at z~4 selected independently of radio spectral index. The QSOs are highly luminous in the optical (eight have M_B_<28, q_0_=0.5, H_0_=50km/s/Mpc). The SEDs are as varied as those seen in optical searches for high-redshift QSOs, but the fraction of objects with weak (strongly self-absorbed) Ly emission is marginally higher (3 out of 18) than for high-redshift QSOs from SDSS (5 out of 96).
- ID:
- ivo://CDS.VizieR/J/MNRAS/449/2818
- Title:
- 87 radio loud quasars (RLS) with 3.6<=z<=4.4
- Short Name:
- J/MNRAS/449/2818
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We obtain a sample of 87 radio-loud quasi-stellar objects (QSOs) in the redshift range 3.6<=z<=4.4 by cross-correlating sources in the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) radio survey (S_1.4GHz_>1mJy) with star-like objects having r<20.2 in Sloan Digital Sky Survey (SDSS) Data Release 7. Of these 87 QSOs, 80 are spectroscopically classified in previous work (mainly SDSS), and form the training set for a search for additional such sources. We apply our selection to 2916 FIRST-DR7 pairs and find 15 likely candidates. Seven of these are confirmed as high-redshift quasars, bringing the total to 87. The candidates were selected using a neural-network, which yields 97 percent completeness (fraction of actual high-z QSOs selected as such) and an efficiency (fraction of candidates which are high-z QSOs) in the range of 47-60 percent. We use this sample to estimate the binned optical luminosity function (LF) of radio-loud QSOs at z~4, and also the LF of the total QSO population and its comoving density. Our results suggest that the radio-loud fraction at high z is similar to that at low z and that other authors may be underestimating the fraction at high z. Finally, we determine the slope of the optical LF and obtain results consistent with previous studies of radio-loud QSOs and of the whole population of QSOs. The evolution of the LF with redshift was for many years interpreted as a flattening of the bright-end slope, but has recently been re-interpreted as strong evolution of the break luminosity for high-z QSOs, and our results, for the radio-loud population, are consistent with this.
- ID:
- ivo://CDS.VizieR/J/MNRAS/390/289
- Title:
- Radio observations of A3158
- Short Name:
- J/MNRAS/390/289
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 1.4- and 2.5-GHz Australia Telescope Compact Array (ATCA) observations of the galaxy cluster A3158 (z=0.0597) which is located within the central part of the Horologium-Reticulum supercluster (HRS). Spectroscopic data for the central part of the HRS suggest that A3158 is in a dynamically important position within the supercluster and that it is moving toward the double cluster system A3125/A3128 which marks the centre of the HRS. A total of 110 radio galaxies are detected in a 35-arcmin radius about the cluster at 1.4GHz, of which 30 are also detected at 2.5GHz.
- ID:
- ivo://CDS.VizieR/J/other/PPMtO/17B.1
- Title:
- Radio properties of ROSAT sources
- Short Name:
- J/other/PPMtO/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A cross-identification of the southern-sky objects with the ROSAT All-Sky Survey (Cat. <IX/10>) and Parkes-MIT-NRAO (PMN) Radio (5GHz) Survey (Cat. <VIII/38>) yields a list of 642 sources. Subsequential optical identification for all these coincidences has been taken to form a large sample of galaxies and Active Galactic Nuclei (AGNs). As a result, 311 (52%) were previously optically identified as extragalactic objects. The fluxes detected from X-ray, optical, and radio bands for them are compiled. This database allows an investigation on broad band energy distribution and other possible correlations among spectral indices and luminosities for various types of extragalactic objects.
- ID:
- ivo://CDS.VizieR/J/MNRAS/444/2498
- Title:
- Radio-Quiet BAL quasars sample
- Short Name:
- J/MNRAS/444/2498
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Studies of radio-loud (RL) broad absorption line (BAL) quasars indicate that popular orientation-based BAL models fail to account for all observations. Are these results extendable to radio-quiet (RQ) BAL quasars? Comparisons of RL and RQ BAL quasars show that many of their properties are quite similar. Here, we extend these analyses to the rest-frame ultraviolet (UV) spectral properties, using a sample of 73 RL and 473 RQ BAL quasars selected from the Sloan Digital Sky Survey. Each RQ quasar is individually matched to an RL quasar in both redshift (over the range 1.5<z<3.5) and continuum luminosity. We compare several continuum, emission line, and absorption line properties, as well as physical properties derived from these measurements. Most properties in the samples are statistically identical, though we find slight differences in the velocity structure of the BALs that cause apparent differences in C iv emission line properties. Differences in the velocities may indicate an interaction between the radio jets and the absorbing material. We also find that UV FeII emission is marginally stronger in RL BAL quasars. All of these differences are subtle, so in general we conclude that RL and RQ BAL QSOs are not fundamentally different objects, except in their radio properties. They are therefore likely to be driven by similar physical phenomena, suggesting that results from samples of RL BAL quasars can be extended to their RQ counterparts.
- ID:
- ivo://CDS.VizieR/J/MNRAS/375/931
- Title:
- Radio sources in the 6dFGS
- Short Name:
- J/MNRAS/375/931
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have identified 7824 radio sources from the 1.4GHz NRAO VLA Sky Survey (NVSS, Cat. <VIII/65>) with galaxies brighter than K=12.75mag in the Second Incremental Data Release of the 6 degree Field Galaxy Survey (6dFGS DR2, Cat. <VII/249>). The resulting sample of redshifts and optical spectra for radio sources over an effective sky area of 7076deg^2^ (about 17 per cent of the celestial sphere) is the largest of its kind ever obtained. NVSS radio sources associated with galaxies in the 6dFGS span a redshift range 0.003<z<0.3 and have median z{bar}=0.043. Through visual examination of 6dF spectra we have identified the dominant mechanism for radio emission from each galaxy. 60 per cent are fuelled by star formation and 40 per cent are fuelled by an active galactic nucleus (AGN) powered by a supermassive black hole. We have accurately determined the local radio luminosity function (RLF) at 1.4GHz for both classes of radio source and have found it to agree well with other recent determinations. From the RLF of star-forming galaxies we derive a local star formation density of 0.022+/-0.001M_{sun}_/yr/Mpc^3^, in broad agreement with recent determinations at radio and other wavelengths.
