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1051. XQ-100 survey neutral gas
ID:
ivo://CDS.VizieR/J/MNRAS/456/4488
Title:
XQ-100 survey neutral gas
Short Name:
J/MNRAS/456/4488
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a sample of 38 intervening damped Lyman {alpha} (DLA) systems identified towards 100 z>3.5 quasars, observed during the XQ-100 survey. The XQ-100 DLA sample is combined with major DLA surveys in the literature. The final combined sample consists of 742 DLAs over a redshift range approximately 1.6<z_abs_<5.0. We develop a novel technique for computing {Omega}_HI_^DLA^ as a continuous function of redshift, and we thoroughly assess and quantify the sources of error therein, including fitting errors and incomplete sampling of the high column density end of the column density distribution function. There is a statistically significant redshift evolution in {Omega}_HI_^DLA^ (>=3{sigma}) from z~2 to z~5. In order to make a complete assessment of the redshift evolution of {Omega}_HI_, we combine our high-redshift DLA sample with absorption surveys at intermediate redshift and 21-cm emission line surveys of the local universe. Although {Omega}_HI_^DLA^, and hence its redshift evolution, remains uncertain in the intermediate-redshift regime (0.1<z_abs_<1.6), we find that the combination of high-redshift data with 21-cm surveys of the local universe all yield a statistically significant evolution in {Omega}_HI_ from z~0 to z~5 (>=3{sigma}). Despite its statistical significance, the magnitude of the evolution is small: a linear regression fit between {Omega}_HI_ and z yields a typical slope of ~0.17x10^-3^, corresponding to a factor of ~4 decrease in {Omega}_HI_ between z=5 and z=0.
1052. XQ-100. X-shooter quasar spectra
ID:
ivo://CDS.VizieR/J/MNRAS/462/3285
Title:
XQ-100. X-shooter quasar spectra
Short Name:
J/MNRAS/462/3285
Date:
21 Oct 2021
Publisher:
CDS
Description:
We statistically study the physical properties of a sample of narrow absorption line (NAL) systems looking for empirical evidences to distinguish between intrinsic and intervening NALs without taking into account any a priori definition or velocity cut-off. We analyse the spectra of 100 quasars with 3.5<z_em_<4.5, observed with X-shooter/Very Large Telescope in the context of the XQ-100 Legacy Survey. We detect an ~8{sigma} excess in the CIV number density within 10000km/s of the quasar emission redshift with respect to the random occurrence of NALs. This excess does not show a dependence on the quasar bolometric luminosity and it is not due to the redshift evolution of NALs. It extends far beyond the standard 5000km/s cut-off traditionally defined for associated absorption lines. We propose to modify this definition, extending the threshold to 10000km/s when weak absorbers (equivalent width <0.2{AA}) are also considered. We infer NV is the ion that better traces the effects of the quasar ionization field, offering the best statistical tool to identify intrinsic systems. Following this criterion, we estimate that the fraction of quasars in our sample hosting an intrinsic NAL system is 33 per cent. Lastly, we compare the properties of the material along the quasar line of sight, derived from our sample, with results based on close quasar pairs investigating the transverse direction. We find a deficiency of cool gas (traced by C II) along the line of sight connected to the quasar host galaxy, in contrast with what is observed in the transverse direction.
1053. X-ray AGN from RASS and SDSS
ID:
ivo://CDS.VizieR/J/AJ/126/2209
Title:
X-ray AGN from RASS and SDSS
Short Name:
J/AJ/126/2209
Date:
21 Oct 2021
Publisher:
CDS
Description:
We describe the initial results of a new program aimed to ultimately yield ~10^4^ fully characterized X-ray source identifications - a sample about an order of magnitude larger than earlier efforts. The technique is detailed and employs X-ray data from the ROSAT All-Sky Survey (RASS, Cat. <IX/10>, <IX/29>) and optical imaging and spectroscopic follow-up from the Sloan Digital Sky Survey (SDSS, <J/AJ/123/567>); these two surveys prove to be serendipitously very well matched in sensitivity. As part of the SDSS software pipelines, optical objects in the SDSS photometric catalogs are automatically positionally cross-correlated with RASS X-ray sources. Then priorities for follow-on SDSS optical spectra of candidate counterparts are automatically assigned using an algorithm based on the known ratios of fX/fopt for various classes of X-ray emitters at typical RASS fluxes of 10^-13^ergs/cm^2^/s. SDSS photometric parameters for optical morphology, magnitude, and colors, plus FIRST radio information, serve as proxies for object class.
1054. X-ray and multiwavelength properties of 11 WLQs
ID:
ivo://CDS.VizieR/J/ApJ/747/10
Title:
X-ray and multiwavelength properties of 11 WLQs
Short Name:
J/ApJ/747/10
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report on the X-ray and multiwavelength properties of 11 radio-quiet quasars with weak or no emission lines identified by the Sloan Digital Sky Survey (SDSS) with redshift z=0.4-2.5. Our sample was selected from the Plotkin et al. catalog (2010, Cat. J/AJ/139/390) of radio-quiet, weak-featured active galactic nuclei (AGNs). The distribution of relative X-ray brightness for our low-redshift weak-line quasar (WLQ) candidates is significantly different from that of typical radio-quiet quasars, having an excess of X-ray weak sources, but it is consistent with that of high-redshift WLQs. Over half of the low-redshift WLQ candidates are X-ray weak by a factor of >~5, compared to a typical SDSS quasar with similar UV/optical luminosity. These X-ray weak sources generally show similar UV emission-line properties to those of the X-ray weak quasar PHL 1811 (weak and blueshifted high-ionization lines, weak semiforbidden lines, and strong UV Fe emission); they may belong to the notable class of PHL 1811 analogs. The average X-ray spectrum of these sources is somewhat harder than that of typical radio-quiet quasars.
1055. X-ray and radio emission of type 1 AGNs
ID:
ivo://CDS.VizieR/J/A+A/545/A66
Title:
X-ray and radio emission of type 1 AGNs
Short Name:
J/A+A/545/A66
Date:
21 Oct 2021
Publisher:
CDS
Description:
X-ray emission from Active Galactic Nuclei (AGN) is dominated by the accretion disk around a supermassive black hole. The radio luminosity, however, has not such a clear origin except in the most powerful sources where jets are evident. The origin (and even the very existence) of the local bi-modal distribution in radio-loudness is also a debated issue. By analysing X-ray, optical and radio properties of a large sample of type 1 AGN and quasars (QSOs) up to z>2, where the bulk of this population resides, we aim to explore the interplay between radio and X-ray emission in AGN, in order to further our knowledge on the origin of radio emission, and its relation to accretion. We analyse a large (~800 sources) sample of type 1 AGN and QSOs selected from the 2XMMi XMM-Newton X-ray source catalogue, cross-correlated with the SDSS DR7 spectroscopic catalogue, covering a redshift range from z~0.3 to z~2.3. Supermassive black hole masses are estimated from the Mg II emission line, bolometric luminosities from the X-ray data, and radio emission or upper limits from the FIRST catalogue. Most of the sources accrete close to the Eddington limit and the distribution in radio-loudness does not appear to have a bi-modal behaviour. We confirm that radio-loud AGN are also X-ray loud, with an X-ray-to-optical ratio up to twice that of radio-quiet objects, even excluding the most extreme strongly jetted sources. By analysing complementary radio-selected control samples, we find evidence that these conclusions are not an effect of the X-ray selection, but are likely a property of the dominant QSO population. Our findings are best interpreted in a context where radio emission in AGN, with the exception of a minority of beamed sources, arises from very close to the accretion disk and is therefore heavily linked to X-ray emission. We also speculate that the radio-loud/radio-quiet dichotomy might either be an evolutionary effect that developed well after the QSO peak epoch, or an effect of incompleteness in small samples.
1056. X-ray and UV parameters of radio-quiet quasars
ID:
ivo://CDS.VizieR/J/ApJ/657/116
Title:
X-ray and UV parameters of radio-quiet quasars
Short Name:
J/ApJ/657/116
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report new Chandra observations of seven optically faint, z~4 radio-quiet quasars (RQQs). We have combined these new observations with previous Chandra observations of RQQs to create a sample of 174 sources. These sources have 0.1<z<4.7, and 10^44^ergs/s<{nu}L_{nu}_(2500{AA})<10^48^ergs/s. The X-ray detection fraction is 90%.
1057. X-ray-bright optically faint AGN
ID:
ivo://CDS.VizieR/J/PASJ/70/S36
Title:
X-ray-bright optically faint AGN
Short Name:
J/PASJ/70/S36
Date:
21 Oct 2021
Publisher:
CDS
Description:
We construct a sample of X-ray-bright optically faint active galactic nuclei by combining Subaru Hyper Suprime-Cam, XMM-Newton, and infrared source catalogs. Fifty-three X-ray sources satisfying i-band magnitude fainter than 23.5mag and X-ray counts with the EPIC-PN detector larger than 70 are selected from 9.1 deg^2^, and their spectral energy distributions (SEDs) and X-ray spectra are analyzed. Forty-four objects with an X-ray to i-band flux ratio FX/Fi>10 are classified as extreme X-ray-to-optical flux sources. Spectral energy distributions of 48 among 53 are represented by templates of type 2 AGNs or star-forming galaxies and show the optical signature of stellar emission from host galaxies in the source rest frame. Infrared/optical SEDs indicate a significant contribution of emission from dust to the infrared fluxes, and that the central AGN is dust obscured. The photometric redshifts determined from the SEDs are in the range of 0.6-2.5. The X-ray spectra are fitted by an absorbed power-law model, and the intrinsic absorption column densities are modest (best-fit logNH=20.5-23.5cm^-2^ in most cases). The absorption-corrected X-ray luminosities are in the range of 6x10^42^-2x10^45^erg/s. Twenty objects are classified as type 2 quasars based on X-ray luminosity and NH. The optical faintness is explained by a combination of redshifts (mostly z>1.0), strong dust extinction, and in part a large ratio of dust/gas.
1058. X-ray emission from quasars
ID:
ivo://CDS.VizieR/J/ApJ/726/20
Title:
X-ray emission from quasars
Short Name:
J/ApJ/726/20
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of an investigation into the X-ray properties of radio-intermediate and radio-loud quasars (RIQs and RLQs, respectively). We combine large, modern optical (e.g., SDSS) and radio (e.g., FIRST) surveys with archival X-ray data from Chandra, XMM-Newton, and ROSAT to generate an optically selected sample that includes 188 RIQs and 603 RLQs. This sample is constructed independently of X-ray properties but has a high X-ray detection rate (85%); it provides broad and dense coverage of the l-z plane, including at high redshifts (22% of objects have z=2-5), and it extends to high radio-loudness values (33% of objects have R*=3-5, using logarithmic units). We measure the "excess" X-ray luminosity of RIQs and RLQs relative to radio-quiet quasars (RQQs) as a function of radio loudness and luminosity, and parameterize the X-ray luminosity of RIQs and RLQs both as a function of optical/UV luminosity and also as a joint function of optical/UV and radio luminosity. RIQs are only modestly X-ray bright relative to RQQs; it is only at high values of radio loudness (R*>~3.5) and radio luminosity that RLQs become strongly X-ray bright.
1059. X-ray of active galaxies and nuclei
ID:
ivo://CDS.VizieR/VII/181
Title:
X-ray of active galaxies and nuclei
Short Name:
VII/181
Date:
21 Oct 2021
Publisher:
CDS
Description:
(no description available)
1060. X-ray, opt. & radio SEDs of Fermi blazars
ID:
ivo://CDS.VizieR/J/ApJS/226/20
Title:
X-ray, opt. & radio SEDs of Fermi blazars
Short Name:
J/ApJS/226/20
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this paper, multiwavelength data are compiled for a sample of 1425 Fermi blazars to calculate their spectral energy distributions (SEDs). A parabolic function, log({nu}F_{nu}_)=P_1_(log{nu}-P_2_)^2^+P_3_, is used for SED fitting. Synchrotron peak frequency (log{nu}_p_), spectral curvature (P_1_), peak flux ({nu}_p_F_{nu}p_), and integrated flux ({nu}F_{nu}_) are successfully obtained for 1392 blazars (461 flat-spectrum radio quasars [FSRQs], 620 BL Lacs [BLs], and 311 blazars of uncertain type [BCUs]; 999 sources have known redshifts). Monochromatic luminosity at radio 1.4GHz, optical R band, X-ray at 1keV and {gamma}-ray at 1GeV, peak luminosity, integrated luminosity, and effective spectral indices of radio to optical ({alpha}_RO_) and optical to X-ray ({alpha}_OX_) are calculated. The "Bayesian classification" is employed to log{nu}_p_ in the rest frame for 999 blazars with available redshift, and the results show that three components are enough to fit the log{nu}_p_ distribution; there is no ultra-high peaked subclass. Based on the three components, the subclasses of blazars using the acronyms of Abdo+ (2010, J/ApJ/716/30) are classified, and some mutual correlations are also studied.