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- 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/574/A121
- Title:
- RXJ2314.9+2243 from radio to X-rays
- Short Name:
- J/A+A/574/A121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Radio-loud narrow-line type 1 galaxies provide us with a fresh look at the blazar phenomenon, the causes of radio loudness, and the physics of jet formation. We present a multi-wavelength study of the radio-loud narrow-line type 1 quasar RX J2314.9+2243, which exhibits some remarkable multi-wavelength properties. It is among the few radio-loud narrow-line type 1 galaxies, with a tentative {gamma}-ray detection, is luminous in the infrared, and shows an exceptionally broad and blueshifted [OIII]{lambda}5007 emission-line component. In order to understand the nature of this source, we have obtained optical, UV, X-ray, and radio observations of RX J2314.9+2243.
- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/601/A32
- Title:
- 10 SALT spectra of HE 0435-4312
- Short Name:
- J/A+A/601/A32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The MgII emission line is visible in the optical band for intermediate redshift quasars (0.4<z<1.6) and it is thus an extremely important tool to measure the black hole mass and to understand the structure of the Broad Line Region. We aim to determine the substructure and the variability of the MgII line with the aim to identify which part of the line comes from a medium in Keplerian motion. Using the Southern African Large Telescope (SALT) with the Robert Stobie Spectrograph (RSS) we performed ten spectroscopic observations of quasar HE 0435-4312 (z=1.2231) over a period of three years (Dec 23/24, 2012 to Dec 7/8, 2015). Both the MgII line and the FeII pseudo-continuum increase with time. We clearly detect the systematic shift of the MgII line with respect to the FeII over the years, corresponding to the acceleration of 104+/-14km/s/year in the quasar rest frame. The MgII line shape is clearly non-Gaussian but single-component, and the increase in line equivalent width and line shift is not accompanied with significant evolution of the line shape. We analyse the conditions in the MgII and FeII formation region and we note that the very large difference in the covering factor and the turbulent velocity also support the conclusion that the two regions are spatially separated. The measured acceleration of the line systematic shift is too large to connect it with the orbital motion at a distance of the Broad Line Region (BLR) in this source. It may imply a precessing inner disk illuminating the BLR. Further monitoring is still needed to better constrain the variability mechanism.
- ID:
- ivo://CDS.VizieR/J/ApJ/804/7
- Title:
- SaMOSA: optical spectroscopy of 7 Fermi blazars
- Short Name:
- J/ApJ/804/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present multi-epoch optical spectroscopy of seven southern Fermi-monitored blazars from 2008 to 2013 using the Small and Medium Aperture Research Telescope System (SMARTS), with supplemental spectroscopy and polarization data from the Steward Observatory. We find that the emission lines are much less variable than the continuum; four of seven blazars had no detectable emission line variability over the 5 yr observation period. This is consistent with photoionization primarily by an accretion disk, allowing us to use the lines as a probe of disk activity. Comparing optical emission line flux with Fermi {gamma}-ray flux and optical polarized flux, we investigate whether relativistic jet variability is related to the accretion flow. In general, we see no such dependence, suggesting that the jet variability is likely caused by internal processes like turbulence or shock acceleration rather than a variable accretion rate. However, three sources showed statistically significant emission line flares in close temporal proximity to very large Fermi {gamma}-ray flares. While we do not have sufficient emission line data to quantitatively assess their correlation with the {gamma}-ray flux, it appears that in some cases the jet might provide additional photoionizing flux to the broad-line region (BLR), which implies that some {gamma}-rays are produced within the BLR, at least for these large flares.
- ID:
- ivo://CDS.VizieR/J/MNRAS/468/77
- Title:
- Sample of confirmed quasar pairs
- Short Name:
- J/MNRAS/468/77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the most precise estimate to date of the clustering of quasars on very small scales, based on a sample of 47 binary quasars with magnitudes of g < 20.85 and proper transverse separations of ~25h^-1^kpc. Our sample of binary quasars, which is about six times larger than any previous spectroscopically confirmed sample on these scales, is targeted using a kernel density estimation (KDE) technique applied to Sloan Digital Sky Survey (SDSS) imaging over most of the SDSS area. Our sample is 'complete' in that all of the KDE target pairs with 17.0<=R<=36.2h^-1^kpc in our area of interest have been spectroscopically confirmed from a combination of previous surveys and our own long-slit observational campaign. We catalogue 230 candidate quasar pairs with angular separations of <8 arcsec, from which our binary quasars were identified. We determine the projected correlation function of quasars (<W>_ p_) in four bins of proper transverse scale over the range 17.0<=R<=36.2h^-1^kpc. The implied small-scale quasar clustering amplitude from the projected correlation function, integrated across our entire redshift range, is A=24.1+/-3.6 at ~26.6h^-1^kpc. Our sample is the first spectroscopically confirmed sample of quasar pairs that is sufficiently large to study how quasar clustering evolves with redshift at ~25h^-1^kpc. We find that empirical descriptions of how quasar clustering evolves with redshift at ~25h^-1^Mpc also adequately describe the evolution of quasar clustering at ~25h^-1^kpc.
- ID:
- ivo://CDS.VizieR/J/MNRAS/508/2798
- Title:
- Sample of 102 distant quasars
- Short Name:
- J/MNRAS/508/2798
- Date:
- 04 Mar 2022 14:51:25
- Publisher:
- CDS
- Description:
- We present the radio properties of optically selected quasars with z>=3. The complete sample consists of 102 quasars with a flux density level S_1.4_>=100mJy in a declination range -35{deg}<=Dec.<=+49{deg}. The observations were obtained in 2017-2020 using the radio telescope RATAN-600. We measured flux densities at six frequencies 1.2, 2.3, 4.7, 8.2, 11.2, and 22GHz quasi-simultaneously with uncertainties of 9-31 per cent. The detection rate is 100, 89, and 46 per cent at 4.7, 11.2, and 22GHz, respectively. We have analysed the averaged radio spectra of the quasars based on the RATAN and literature data. We classify 46 per cent of radio spectra as peaked-spectrum, 24 per cent as flat, and none as ultra-steep spectra ({alpha}<=-1.1). The multifrequency data reveal that a peaked spectral shape (PS) is a common feature for bright high-redshift quasars. This indicates the dominance of bright compact core emission and the insignificant contribution of extended optically thin kpc-scale components in observed radio spectra. Using these new radio data, the radio loudness log R was estimated for 71 objects with a median value of 3.5, showing that the majority of the quasars are highly radio-loud with log R>2.5. We have not found any significant correlation between z and {alpha}. Several new megahertz- peaked spectrum (MPS) and gigahertz- peaked spectrum (GPS) candidates are suggested. Further studies of their variability and additional low-frequency observations are needed to classify them precisely.
- ID:
- ivo://CDS.VizieR/J/other/RAA/16.13
- Title:
- Sample of Fermi Blazars
- Short Name:
- J/other/RAA/16.1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the {gamma}-ray luminosity and beaming effect for Fermi blazars. Our results are as follows. (i) There are significant correlations between {gamma}-ray luminosity and radio core luminosity, and between {gamma}-ray luminosity and Rv, which suggests that the {gamma}-ray emissions have a strong beaming effect. (ii) Using the Lext/Mabs as an indicator of environment effects, we find that there is no significant correlation between {gamma}-ray luminosity and Lext/Mabs for all sources when we remove the effect of redshift. Flat spectrum radio quasars considered alone also do not show a significant correlation, but BL Lacertae objects (BL Lacs) still show a significant correlation when we remove the effect of redshift. These results suggest that the {gamma}-ray emission may be affected by the environment on a kiloparsec scale for BL Lacs.
