- ID:
- ivo://CDS.VizieR/J/ApJ/688/826
- Title:
- Radio and X-ray-emitting broad-line AGNs
- Short Name:
- J/ApJ/688/826
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use a recently released SDSS catalog of X-ray-emitting AGNs in conjunction with the FIRST radio survey to investigate the black hole (BH) fundamental plane relationship between the 1.4GHz radio luminosity (L_r_), 0.1-2.4keV X-ray luminosity (L_X_), and black hole mass (M), namely, logL_r_={xi}_RX_logL_X_+{xi}_RM_logM+constant. For this purpose, we compile a large sample of 725 broad-line AGNs, which consists of 498 radio-loud sources and 227 radio-quiet sources. We confirm that radio-loud objects have a steeper slope ({xi}_RX_) with respect to radio-quiet objects and that the dependence of the BH fundamental plane on the BH mass ({xi}_RM_) is weak.
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- ID:
- ivo://CDS.VizieR/VIII/108
- Title:
- Radio core dominance of Fermi/LAT-detected AGNs
- Short Name:
- VIII/108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of 4388 AGNs with available radio core-dominance parameters-defined as the ratio of the core flux densities to the extended ones, R=S_core_/S_ext._ - which includes 630 Fermi-detected AGNs from the fourth source catalog (4FGL) of the Fermi Large Area Telescope (Fermi/LAT); the rest are non-Fermi-detected AGNs. In our sample, 584 blazars are Fermi-detected and 1310 are not. The sample also contains other subclasses, such as Seyferts, Fanaroff-Riley I/II galaxies, and normal galaxies. We investigate various properties of the Fermi-detected and non-Fermi-detected AGNs by using core-dominance parameters, capitalizing on a previous study which showed that R is a good indicator of beaming. We then calculate radio spectral indices for the whole sample, and adopt {gamma}-ray-photon indices for the Fermi AGNs from the 4FGL catalog to discuss the properties of different subclasses. We obtain a relation between the core-dominance parameters and the radio spectral indices for both Fermi and non-Fermi sources, assuming a two-component model in the radio band. Our previous study ruled out the assumption that the core-dominance parameters and radio spectral indices are quite different for different AGN subclasses. This holds not only for Fermi sources but also for non-Fermi sources. In particular, R is, on average, greater for the former AGNs than for the latter. In this study, we enlarge our sample with available values of R to 4388 AGNs, and the obtained conclusions are consistent with our previous study. We assume that the same two-component model holds for the {gamma}-ray band as for the radio band, and therefore, adopt the same relation between the core-dominance parameters and the {gamma}-ray-photon indices for Fermi AGNs. Our fitting results indicate that the {gamma}-ray emissions of Fermi blazars originate mainly from the jet, and therefore, we conclude that the Fermi blazars are beamed.
- ID:
- ivo://CDS.VizieR/J/MNRAS/478/3848
- Title:
- Radio-emitting AGN environmental prop.
- Short Name:
- J/MNRAS/478/3848
- Date:
- 10 Dec 2021 00:52:31
- Publisher:
- CDS
- Description:
- We study the environmental properties of z<=1.2 radio-selected active galactic nuclei (AGNs) belonging to the ~2deg^2^ of the COSMOS field, finding that about 20 per cent of them appear within overdense structures. AGNs with P_1.4GHz_>10^23.5^W/Hz/sr are twice more likely to be found in clusters with respect to fainter sources (~38 per cent vs ~15 per cent), just as radio-selected AGNs with stellar masses M_*_>10^11^M_{sun}_ are twice more likely to be found in overdense environments with respect to objects of lower mass (~24 per cent vs ~11 per cent). Comparisons with galaxy samples further suggest that radio-selected AGN of large stellar mass tend to avoid underdense environments more than normal galaxies with the same stellar content. Stellar masses also seem to determine the location of radio-active AGN within clusters: ~100 per cent of the sources found as satellite galaxies have M_*_<10^11.3^M_{sun}_, while ~100 per cent of the AGNs coinciding with a cluster central galaxy have M_*_>10^11^M_{sun}_. No different location within the cluster is instead observed for AGN of various radio luminosities. Radio AGN, which also emit in the Mid-Infrared show a marked preference to be found as isolated galaxies (~70 per cent) at variance with those also active in the X-ray that all seem to reside within overdensities. What emerges from our work is a scenario whereby physical processes on sub-pc and kpc scales (e.g. emission, respectively, related to the AGN and to star formation) are strongly interconnected with the large-scale environment of the AGN itself.
- ID:
- ivo://CDS.VizieR/J/A+A/303/420
- Title:
- Radio galaxies and quasars
- Short Name:
- J/A+A/303/420
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The simple unification scheme of powerful radio galaxies and quasars, based entirely on the orientation dependent effects, has been confronted with the observed radio structures for 152 radio galaxies and 173 steep spectrum quasars. Contrary to the scheme's prediction, the cosmological evolution of geometrical parameters describing the large scale structure of these two types of radio sources are different.
- ID:
- ivo://CDS.VizieR/J/MNRAS/333/100
- Title:
- Radio galaxies in the 2dFGRS
- Short Name:
- J/MNRAS/333/100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use redshift determinations and spectral analysis of galaxies in the 2dF Galaxy Redshift Survey (<VII/226>) to study the properties of local radio sources with S>=1mJy. 557 objects (hereafter called the spectroscopic sample) drawn from the FIRST survey(<VIII/71>) , corresponding to 2.3 per cent of the total radio sample, are found in the 2dFGRS catalogue within the area 9h 48min<=RA<=14h 32min and -2.77{deg}<=DE<=2.25{deg} (2000), down to a magnitude limit b_J_=19.45. The excellent quality of 2dF spectra allows us to divide these sources into classes, according to their optical spectra.
- ID:
- ivo://CDS.VizieR/J/ApJ/741/30
- Title:
- Radio/{gamma}-ray correlation in AGN
- Short Name:
- J/ApJ/741/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed statistical analysis of the correlation between radio and gamma-ray emission of the active galactic nuclei (AGNs) detected by Fermi during its first year of operation, with the largest data sets ever used for this purpose. We use both archival interferometric 8.4GHz data (from the Very Large Array and ATCA, for the full sample of 599 sources) and concurrent single-dish 15GHz measurements from the Owens Valley Radio Observatory (OVRO, for a sub sample of 199 objects). Our unprecedentedly large sample permits us to assess with high accuracy the statistical significance of the correlation, using a surrogate data method designed to simultaneously account for common-distance bias and the effect of a limited dynamical range in the observed quantities.
- ID:
- ivo://CDS.VizieR/J/ApJ/481/95
- Title:
- Radio identification of EGRET sources
- Short Name:
- J/ApJ/481/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a method to assess the reliability of the identification of EGRET sources with extragalactic radio sources. We verify that EGRET is detecting the blazar class of active galactic nuclei (AGNs). However many published identifications are found to be questionable. We provide a table of 42 blazars that we expect to be robust identifications of EGRET sources. This includes one previously unidentified EGRET source, the lensed AGN PKS 1830-210, near the direction of the Galactic center. We provide the best available positions for 16 more radio sources that are also potential identifications for previously unidentified EGRET sources. All high Galactic latitude EGRET sources (|b|>3) that demonstrate significant variability can be identified with flat-spectrum radio sources. This suggests that EGRET is not detecting any type of AGN other than blazars. This identification method has been used to establish with 99.998% confidence that the peak gamma-ray flux of a blazar is correlated with its average 5GHz radio flux. An even better correlation is seen between gamma-ray flux and the 2.29GHz flux density measured with VLBI at the base of the radio jet. Also, using high-confidence identifications, we find that the radio sources identified with EGRET sources have greater correlated VLBI flux densities than the parent population of flat radio spectrum sources.
- ID:
- ivo://CDS.VizieR/J/A+A/575/A55
- Title:
- Radio jet emission from GeV-emitting NLSy1
- Short Name:
- J/A+A/575/A55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With the current study we aim at gaining understanding on the properties of radio emission and the assumed jet from four radio loud and {gamma}-ray loud Narrow Line Seyfert 1 galaxies i.e. Seyfert 1 galaxies with emission lines at the low-end of the FWHM distribution. The ultimate goal is twofold; first, the investigation whether a relativistic jet is operating at the source giving out the radio output observed and second, the quantification of the jet characteristics in order to understand possible similarities and differences with the jets found in typical blazars. The current study relies on the most systematic monitoring of radio loud and {gamma}-ray detected Narrow Line Seyfert 1 galaxies in the cm and mm radio bands conducted with the Effelsberg 100-m and IRAM 30-m telescopes. It covers the longest time baselines and the most radio frequencies, to date. This dataset of multi- wavelength, long-term radio light curves is analysed from a number of perspectives. A novel algorithm is introduced in order to extract sensible variability parameters (mainly amplitudes and timescales) which are then used for the computation of variability brightness temperatures and the corresponding Doppler factors. The jet powers are computed from the light curves to estimate the energy output and compare it with typical blazars. The dynamics of radio Spectra Energy Distributions are examined for understanding the mechanism causing the variability. The length of the available light curves for 3 of the 4 sources in the sample allowed a firm understanding of the general behaviour of the sources. They all display intensive variability which seems to be happening at a pace rather faster than what is generally seen in blazars. The flaring events become progressively more prominent as the frequency increases and show intensive spectral evolution indicative of shock evolution. The variability brightness temperatures and the associated Doppler factors are rather moderate implying a mildly relativistic jet. The computed jet powers show very energetic flows. The radio polarisation in one case, clearly implies the presence of a quiescent jet underlying recursive flaring activity. Finally, in one case, the sudden disappearance of a {gamma}-ray flare below some critical frequency in our band, urges for further investigation of the possible mechanism causing the evolution of broadband events. Despite the generally lower flux densities the sources appear to show all typical characteristics seen in blazars powered by relativistic jets. Intensive variability, spectral evolution across the different bands following evolutionary paths explained by traveling shocks, Doppler factors indicating mildly relativistic speeds.
- ID:
- ivo://CDS.VizieR/J/A+A/596/A45
- Title:
- Radio light curves of 8 AGN
- Short Name:
- J/A+A/596/A45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To fully exploit the scientific potential of the Fermi mission for the physics of active galactic nuclei (AGN), we initiated the F-GAMMA programme. Between 2007 and 2015 the F-GAMMA was the prime provider of complementary multi-frequency monitoring in the radio regime. Aims. We quantify the radio variability of {gamma}-ray blazars. We investigate its dependence on source class and examine whether the radio variability is related to the {gamma}-ray loudness. Finally, we assess the validity of a putative correlation between the two bands. Methods. The F-GAMMA performed monthly monitoring of a sample of about 60 sources at up to twelve radio frequencies between 2.64 and 228.39GHz. We perform a time series analysis on the first 2.5-yr data set to obtain variability parameters. A maximum likelihood analysis is used to assess the significance of a correlation between radio and {gamma}-ray fluxes. We present light curves and spectra (coherent within ten days) obtained with the Effelsberg 100m and IRAM 30m telescopes. All sources are variable across all frequency bands with amplitudes increasing with frequency up to rest frame frequencies of around 60-80GHz as expected by shock-in-jet models. Compared to flat-spectrum radio quasars (FSRQs), BL Lacertae objects (BL Lacs) show systematically lower variability amplitudes, brightness temperatures, and Doppler factors at lower frequencies, while the difference vanishes towards higher ones. The time scales appear similar for the two classes. The distribution of spectral indices appears flatter or more inverted at higher frequencies for BL Lacs. Evolving synchrotron self-absorbed components can naturally account for the observed spectral variability. We find that the Fermi-detected sources show larger variability amplitudes, brightness temperatures, and Doppler factors than non-detected ones. Flux densities at 86.2 and 142.3GHz correlate with 1GeV fluxes at a significance level better than 3{sigma}, implying that {gamma} rays are produced very close to the mm-band emission region.
- 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.
