- ID:
- ivo://CDS.VizieR/VII/158
- Title:
- Revised and Updated Catalog of Quasi-stellar Objects
- Short Name:
- VII/158
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is a catalog of all known quasi-stellar objects (QSO's) with measured emission redshifts and BL Lac objects, complete to 1992 December 31. The catalog contains 7312 objects, nearly all QSOs including about 90 BL Lac objects. The catalog and references contain extensive information on names, positions, magnitudes, color, emission-line redshifts, absorption, variability, polarization, and X-ray, radio, and infrared data. A key in the form of subsidiary tables enables the reader to relate the name of a given object to its coordinate name which is used throughout the catalog.
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- ID:
- ivo://CDS.VizieR/J/A+AS/128/153
- Title:
- Revised GB/GB2 sample of radio sources
- Short Name:
- J/A+AS/128/153
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The revised sample of 373 extragalactic radio sources brighter than 0.2 Jy at 1.4GHz is presented. These sources, selected from the finding Green Bank surveys, were mapped at 1465 MHz using the VLA at different configurations. The biases introduced into the original GB (Maslowski, 1972AcA....22..227M) and GB2 (Machalski, 1978AcA....28..367M) catalogues by confusion as well as partial resolution by the VLA at its A-configuration, are eliminated. In effect, a number of sources have been excluded, and a few other are included into the revised sample. Now the sample is about 99, 97 and 95 per cent complete for sources with S_1.4_>=0.55Jy, 0.25Jy<=S_1.4_<0.55Jy, and 0.2Jy<=S_1.4_<0.25Jy, respectively. Table 3 gives the compilation of the radio, optical, and X-ray data available for the sample sources.
- ID:
- ivo://CDS.VizieR/J/ApJ/841/113
- Title:
- Roma-BZCAT synchroton peak & Compton dominance
- Short Name:
- J/ApJ/841/113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate a sample of 622 blazars with measured fluxes at 12 wavebands across the radio-to-gamma-ray spectrum but without spectroscopic or photometric redshifts. This sample includes hundreds of sources with newly analyzed X-ray spectra reported here. From the synchrotron peak frequencies, estimated by fitting the broadband spectral energy distributions (SEDs), we find that the fraction of high-synchrotron-peaked blazars in these 622 sources is roughly the same as in larger samples of blazars that do have redshifts. We characterize the no-redshift blazars using their infrared colors, which lie in the distinct locus called the WISE blazar strip, then estimate their redshifts using a KNN regression based on the redshifts of the closest blazars in the WISE color-color plot. Finally, using randomly drawn values from plausible redshift distributions, we simulate the SEDs of these blazars and compare them to known blazar SEDs. Based on all these considerations, we conclude that blazars without redshift estimates are unlikely to be high-luminosity, high- synchrotron-peaked objects, which had been suggested in order to explain the "blazar sequence"-an observed trend of SED shape with luminosity-as a selection effect. Instead, the observed properties of no-redshift blazars are compatible with a causal connection between jet power and electron cooling, i.e., a true blazar sequence.
- ID:
- ivo://CDS.VizieR/J/A+A/319/413
- Title:
- ROSAT detected quasars. I.
- Short Name:
- J/A+A/319/413
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have compiled a sample of all quasars with measured radio emission from the Veron-Cetty - Veron catalogue (1993, VV93 <VII/166>) detected by ROSAT in the ALL-SKY SURVEY (RASS, Voges 1992), as targets of pointed observations, or as serendipitous sources from pointed observations as publicly available from the ROSAT point source catalogue (ROSAT-SRC, Voges et al. 1995). The total number of ROSAT detected radio quasars from the above three sources is 654 objects. 69 of the objects are classified as radio-quiet using the defining line at a radio-loudness of 1.0, and 10 objects have no classification. The 5GHz data are from the 87GB radio survey, the NED database, or from the Veron-Cetty - Veron catalogue. The power law indices and their errors are estimated from the two hardness ratios given by the SASS assuming Galactic absorption. The X-ray flux densities in the ROSAT band (0.1-2.4keV) are calculated from the count rates using the energy to counts conversion factor for power law spectra and Galactic absorption. For the photon index we use the value obtained for a individual source if the estimated 1 sigma error is smaller than 0.5, otherwise we use the mean value 2.14.
- ID:
- ivo://CDS.VizieR/J/A+A/323/739
- Title:
- ROSAT detected quasars. II.
- Short Name:
- J/A+A/323/739
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the broad band, radio - to - X-ray, properties of a large sample of mostly previously optically unidentified radio-loud X-ray sources from the correlation of a ROSAT All-Sky Survey source list with the 5GHz Green Bank Survey of the northern sky (RGB sample) which is one of the largest well-defined flux-limited surveys of AGN ever obtained. Further, the RGB pushes 1-2 orders of magnitude deeper in both X-ray and radio flux compared to previous unbiased wide-area AGN surveys. Follow up VLA observations of the candidate objects yielded positions with arcsec accuracy which were used to find optical counterparts to the sources from digitized POSS plates. The sources are divided into three classes according to the positional offset between the X-ray and radio candidates and the spatial resolution of the radio observations, reflecting the various degrees of confidence about the correctness of the proposed association. Although the nature of the sources as well as their redshifts remain to be determined in spectroscopic follow up observations, the derived flux ratios lead to the conclusion that the majority of them are quasars. Hardly any correlations could be found between different source parameters, possibly due to the fact that most of the objects are found in a relatively small flux range near the sensitivity limit of the radio catalogue. The majority of the new RGB sources have broad-band properties between those of traditional radio-selected and X-ray selected AGN. There is no bimodal distribution in the radio-loudness distribution, and the traditional division between radio-quiet and radio-loud AGN may not be warranted.
- ID:
- ivo://CDS.VizieR/J/A+A/330/108
- Title:
- ROSAT detected quasars. II.
- Short Name:
- J/A+A/330/108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have compiled a sample of all radio-quiet quasars or quasars without radio detection from the Veron-Cetty - Veron catalogue (1993, VV93, Cat. <VII/166>) detected by ROSAT in the ALL-SKY SURVEY (RASS, Voges 1992, in Proc. of the ISY Conference `Space Science', ESA ISY-3, ESA Publications, p.9, See Cat. <IX/10>), as targets of pointed observations, or as serendipitous sources from pointed observations publicly available from the ROSAT point source catalogue (ROSAT-SRC, Voges et al. 1995, Cat. <IX/11>). For all sources we used the results of the Standard Analysis Software System (SASS, Voges et al. 1992, in Proc. of the ISY Conference `Space Science', ESA ISY-3, ESA Publications, p.223), employing the most recent processing for the Survey data (RASS-II, Voges et al. 1996, Cat. <IX/10>). The total number of quasars is 846. 69 of the radio-quiet objects with radio detections have already been presented in a previous paper (Brinkmann, Yuan, & Siebert 1997, Cat. <J/A+A/319/413>) using the RASS-I results. 17 objects were found to be radio-loud from recent radio surveys and were marked in the table. When available, the power law photon indices and the corresponding absorption column densities (NH) were estimated from the two hardness ratios given by the SASS, both with free fitted NH and for Galactic absorption. The unabsorbed X-ray flux densities in the ROSAT band (0.1-2.4keV) were calculated from the count rates using the energy to counts conversion factor for power law spectra and Galactic absorption. As the photon index we used the value obtained for the individual source if the estimated 1-{sigma} error is smaller than 0.5, otherwise we used the redshift-dependent mean value (see the paper for details).
- ID:
- ivo://CDS.VizieR/J/A+A/371/833
- Title:
- ROSAT Ultra Deep Survey
- Short Name:
- J/A+A/371/833
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ROSAT Ultra Deep Survey in the Lockman Hole consists of a sample of 94 X-ray sources reaching a limiting flux of 1.2x10-15erg/s/cm^2^ in the 0.5-2.0keV energy band. About 90% of the X-ray sources have been spectroscopically identified using low-resolution Keck spectra.
- ID:
- ivo://CDS.VizieR/J/MNRAS/442/3329
- Title:
- Rotation measures of 2642 quasars
- Short Name:
- J/MNRAS/442/3329
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained the rotation measures (RMs) of 2642 quasars by using cross-identification of the most updated quasar catalogue and the RM catalogue. After discounting the foreground Galactic Faraday rotation of the Milky Way, we obtain the residual rotation measure (RRM) of these quasars. We have carefully discarded the effects from measurement and systematical uncertainties of RRMs as well as large RRMs from RM outliers, and we have obtained marginal evidence for the redshift evolution of the real dispersion of RRMs which steadily increases to 10rad/m^2^ about z~1 and is saturated at higher redshifts. Ionized clouds in the form of galaxy halos, galaxy clusters or cosmological filaments with different RM dispersion widths could produce the observed RRM evolutions. However, current data sets cannot constrain the contributions from galaxy halos and cosmic webs. Future measurements of RMs for a large sample of quasars with high precision are necessary to disentangle these different contributions.
- ID:
- ivo://CDS.VizieR/J/A+A/472/699
- Title:
- ROXA: multi-frequency large sample of blazars
- Short Name:
- J/A+A/472/699
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Although Blazars are a small fraction of the overall AGN population they are expected to be the dominant population of extragalactic sources in the hard X-ray and gamma-ray bands and have been shown to be the largest contaminant of CMB fluctuation maps. So far the number of known blazars is of the order of several hundreds, but the forthcoming AGILE, GLAST and Planck space observatories will detect several thousand of objects of this type. In preparation for these missions it is necessary to identify new samples of blazars to study their multi-frequency characteristics and statistical properties. We compiled a sample of objects with blazar-like properties via a cross-correlation between large radio (NVSS, ATCAPMN) and X-ray surveys (RASS) using the SDSS-DR4 and 2dF survey data to spectroscopically identify our candidates and test the validity of the selection method. We present the Radio-Optical-X-ray catalog built at ASDC (ROXA), a list of 816 objects among which 510 are confirmed blazars. Only 19% of the candidates turned out to be certainly non-blazars demonstrating the high efficiency of our selection method. Our catalog includes 173 new blazar identifications, or about 10% of all presently known blazars. The relatively high flux threshold in the X-ray energy band (given by the RASS survey) preferentially selects objects with high FX/Fr ratio leading to the discovery of new High Energy Peaked BL Lac (HBLs).Our catalog therefore includes many new potential targets for GeV-TeV observations.
- ID:
- ivo://CDS.VizieR/J/A+A/642/A153
- Title:
- SAGAN. I. New sample & multi-wavelength studies
- Short Name:
- J/A+A/642/A153
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results of a project called SAGAN, which is dedicated solely to the studies of relatively rare megaparsec-scale radio galaxies in the Universe, called giant radio galaxies (GRGs). We have identified 162 new GRGs primarily from the NVSS with sizes ranging from ~0.71Mpc to 2.82Mpc in the redshift range of ~0.03-0.95, of which 23 are hosted by quasars (giant radio quasars, GRQs). As part of the project SAGAN, we have created a database of all known GRGs, the GRG catalogue, from the literature (including our new sample); it includes 820 sources. For the first time, we present the multi-wavelength properties of the largest sample of GRGs. Our results establish that the distributions of the radio spectral index and the black hole mass of GRGs do not differ from the corresponding distributions of normal-sized radio galaxies (RGs). However, GRGs have a lower Eddington ratio (ER) than RGs. Using the mid-infrared data, we classified GRGs in terms of their accretion mode: either a high-power radiatively efficient high-excitation state, or a radiatively inefficient low-excitation state. We find that GRGs in high-excitation state statistically have larger sizes, stronger radio power, jet kinetic power, and higher ER than those in low-excitation state. Our analysis reveals a strong correlation between the ER and the scaled jet kinetic power, which suggests a disc-jet coupling. Our environmental study reveals that ~10% of all GRGs may reside at the centres of galaxy clusters, in a denser galactic environment, while the majority appears to reside in a sparse environment. We find that the probability of BCG as a GRG is quite low. We present new results for GRGs that range from black hole mass to large-scale environment properties. We discuss their formation and growth scenarios, highlighting the key physical factors that cause them to reach their gigantic size.
