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631. Properties of weak emission-line QSOs (WLQ)
ID:
ivo://CDS.VizieR/J/ApJ/696/580
Title:
Properties of weak emission-line QSOs (WLQ)
Short Name:
J/ApJ/696/580
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present Chandra observations of nine high-redshift quasars (z=2.7-5.9) discovered by the Sloan Digital Sky Survey with weak or undetectable high-ionization emission lines in their UV spectra (WLQs). Adding archival X-ray observations of six additional sources of this class has enabled us to place the strongest constraints yet on the X-ray properties of this remarkable class of active galactic nuclei (AGNs). Although our data cannot rule out the possibility that the emission lines are overwhelmed by a relativistically boosted continuum, as manifested by BL Lac objects, we find that WLQs are considerably weaker in the X-ray and radio bands than the majority of BL Lacs found at much lower redshifts. If WLQs are high-redshift BL Lacs, then it is difficult to explain the lack of a large parent population of X-ray and radio bright weak-lined sources at high redshift. We also consider the possibility that WLQs are quasars with extreme properties, and in particular that the emission lines are suppressed by high accretion rates. Using joint spectral fitting of the X-ray spectra of 11 WLQs, we find that the mean photon index in the hard X-ray band is consistent with those observed in typical radio-quiet AGNs with no hint of an unusually steep hard-X-ray spectrum. This result poses a challenge to the hypothesis that WLQs have extremely high accretion rates, and we discuss additional observations required to test this idea.
632. Proximate damped Ly{alpha} systems in SDSS-DR5
ID:
ivo://CDS.VizieR/J/ApJ/675/1002
Title:
Proximate damped Ly{alpha} systems in SDSS-DR5
Short Name:
J/ApJ/675/1002
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using the Sloan Digital Sky Survey Data Release 5 (SDSS-DR5), we survey proximate damped Ly{alpha} systems (PDLAs): absorption-line systems with HI column density N_H_>=2x10^20^cm^-2^ at velocity separation {delta}v<2999km/s from their background quasar. Many of these absorbers may be physically associated with their background quasars, and their statistics allow us to study quasar environments out to z~5. However, the large ionizing flux emitted by a quasar can ionize the neutral gas in a nearby galaxy, possibly giving rise to a "proximity effect", analogous to the similar effect observed in the Ly{alpha} forest. From a sample of 108 PDLAs, we measure the HI frequency distribution f(N_H_,X) incidence, and gas mass density of the PDLAs near luminous quasars over the redshift interval z=2.2-5. The incidence and mass density of PDLAs at z~3 is approximately twice that of intervening DLAs, while at z<2.5 and >3.5 the f(N_H_X) distribution is enhanced but statistically consistent with the intervening population. We interpret the observed enhancement of PDLAs around quasars in terms of quasar-galaxy clustering and compare the strength of the clustering signal to the expectation from independent measures of the respective clustering strengths of DLAs and quasars, as well as a complementary analysis of the clustering of absorbers around quasars in the transverse direction. We find that there are a factor of 5-10 fewer PDLAs around quasars than expected and interpret this result as evidence for the hypothesis that the ionizing flux from the quasars photoevaporates HI in nearby DLA galaxies, thus reducing their cross section for DLA absorption. This constitutes the first detection of a "proximity effect" for DLAs.
633. PS1 photometry of 2863 ICRF3 quasars
ID:
ivo://CDS.VizieR/J/AJ/162/21
Title:
PS1 photometry of 2863 ICRF3 quasars
Short Name:
J/AJ/162/21
Date:
14 Mar 2022 06:53:33
Publisher:
CDS
Description:
We make use of individual (epoch) detection data from the Pan-STARRS "3{pi}" survey for 2863 optical ICRF3 counterparts in the five wavelength bands g, r, i, z, and y, published as part of the Data Release 2. A dedicated method based on the Functional Principal Component Analysis is developed for these sparse and irregularly sampled data. With certain regularization and normalization constraints, it allows us to obtain uniform and compatible estimates of the variability amplitudes and average magnitudes between the passbands and objects. We find that the starting assumption of affinity of the light curves for a given object at different wavelengths is violated for several percent of the sample. The distributions of rms variability amplitudes are strongly skewed toward small values, peaking at ~0.1mag with tails stretching to 2mag. Statistically, the lowest variability is found for the r band and the largest for the reddest y band. A small "brighter-redder" effect is present, with amplitudes in y greater than amplitudes in g in 57% of the sample. The variability versus redshift dependence shows a strong decline with z toward redshift 3, which we interpret as the time dilation of the dominant time frequencies. The colors of radio-loud ICRF3 quasars are correlated with redshift in a complicated, wavy pattern governed by the emergence of brightest emission lines within the five passbands.
634. PS1 z>5.6 quasars follow-up
ID:
ivo://CDS.VizieR/J/ApJS/227/11
Title:
PS1 z>5.6 quasars follow-up
Short Name:
J/ApJS/227/11
Date:
21 Oct 2021
Publisher:
CDS
Description:
Luminous quasars at z>5.6 can be studied in detail with the current generation of telescopes and provide us with unique information on the first gigayear of the universe. Thus far, these studies have been statistically limited by the number of quasars known at these redshifts. Such quasars are rare, and therefore, wide-field surveys are required to identify them, and multiwavelength data are required to separate them efficiently from their main contaminants, the far more numerous cool dwarfs. In this paper, we update and extend the selection for the z~6 quasars presented in Banados+ (2014AJ....148...14B) using the Pan-STARRS1 (PS1) survey. We present the PS1 distant quasar sample, which currently consists of 124 quasars in the redshift range 5.6<~z<~6.7 that satisfy our selection criteria. Of these quasars, 77 have been discovered with PS1, and 63 of them are newly identified in this paper. We present the composite spectra of the PS1 distant quasar sample. This sample spans a factor of ~20 in luminosity and shows a variety of emission line properties. The number of quasars at z>5.6 presented in this work almost doubles the previously known quasars at these redshifts, marking a transition phase from studies of individual sources to statistical studies of the high-redshift quasar population, which was impossible with earlier, smaller samples.
635. QJ0643-5041 UVES spectra
ID:
ivo://CDS.VizieR/J/A+A/562/A88
Title:
QJ0643-5041 UVES spectra
Short Name:
J/A+A/562/A88
Date:
21 Oct 2021
Publisher:
CDS
Description:
Molecular hydrogen in the interstellar medium (ISM) of high-redshift galaxies can be detected directly from its UV absorptions imprinted in the spectrum of background quasars. Associated absorptions from HI and metals allow for the study of the chemical enrichment of the gas, while the analysis of excited species and molecules make it possible to infer the physical state of the ISM gas. In addition, given the numerous H_2_ lines usually detected, these absorption systems are unique tools to constrain the cosmological variation of the proton-to-electron mass ratio, {mu}. We intend to study the chemical and physical state of the gas in the H_2_-bearing cloud at z_abs_=2.658601 towards the quasar QJ0643-5041 (z_em_=3.09) and to derive a useful constraint on the variation of {mu}. We use high signal-to-noise ratio, high-resolution VLT-UVES data of QJ0643-5041 amounting to a total of more than 23 hours exposure time and fit the HI, metals, and H_2_ absorption features with multiple-component Voigt profiles. We study the relative populations of H_2_ rotational levels and the fine-structure excitation of neutral carbon to determine the physical conditions in the H_2_-bearing cloud.
636. QORG catalog of radio/X-ray sources
ID:
ivo://CDS.VizieR/J/A+A/427/387
Title:
QORG catalog of radio/X-ray sources
Short Name:
J/A+A/427/387
Date:
21 Oct 2021
Publisher:
CDS
Description:
The QUASARS.ORG Catalogues align and overlay the year 2001/2 releases of the ROSAT HRI, RASS, PSPC and WGA X-ray catalogues, the NVSS (2002), FIRST (2003) and SUMSS (2003) radio catalogues, the Veron QSO catalogue (2003) and various galaxy/star reference catalogues onto the optical APM and USNO-A catalogues. These catalogues display calculated percentage probabilities for each optical radio/X-ray associated object of its likelihood of being a quasar, galaxy, star, or erroneous radio/X-ray association. The main Master catalogue (master.dat) displays all 501,761 radio/X-ray associated optical objects and known quasars which are optically detected in APM/USNO-A. Up to six radio/X-ray catalog identifications are presented for each optical object, plus any double radio lobes (21,498 of these). These are superimposed (and laterally fitted) onto a 670,925,779-object optical background which combines APM and USNO-A data. The Free-Lunch catalogue is a concise easy-to-read variant of the Master catalogue showcasing just one X-ray and/or radio identification for each object. This catalogue is the original version which was publicized to show astronomers that there *is* a free lunch after all! There is also a subset catalogue of QSO candidates, and a subset catalogue of known QSOs/galaxies/stars. Objects presented in this catalogue are those optical APM/USNO-A objects which are associated with X-ray/radio detections, or any optically-found catalogued QSO/AGN/Bl Lac objects, with confidence >40% of being a radio/X-ray emitting optical object. There are 501,761 objects included in all (including 48,285 catalogued quasars), representing the 99.4% coverage of the sky available from the APM and USNO-A. Each object is shown as one line bearing the position in equatorial coordinates, red and blue optical magnitudes (recalibrated) and PSF class, calculated probabilities of the object being, separately, a quasar, galaxy, star, or erroneous radio/X-ray association, any radio identification from each of the NVSS, FIRST and SUMSS surveys, including candidate double-lobe detections, any X-ray identification from each of the ROSAT HRI, RASS, PSPC and WGA surveys, including fluxes and field shifts of those identifications, plus, if already catalogued, the object name and redshift where applicable. The QORG catalogue and supporting data can be accessed from the catalogue home page at http://quasars.org/qorg-data.htm Questions or comments may be directed to eric@flesch.org
637. 5 QPE X-ray sources spectra
ID:
ivo://CDS.VizieR/J/A+A/659/L2
Title:
5 QPE X-ray sources spectra
Short Name:
J/A+A/659/L2
Date:
04 Mar 2022 06:38:31
Publisher:
CDS
Description:
We perform a systematic study of the five known QPE host galaxies with the aim of providing new insights into their nature. We analyse new and archival medium resolution optical spectroscopy of the QPE hosts. We measure emission (and absorption) line fluxes, their ratios and equivalent widths (EWs), to locate the QPE hosts on diagnostic diagrams. We also measure the velocity dispersion of the stellar absorption lines to estimate their black hole masses. All QPE host galaxies show emission lines in their optical spectra. Based on their ratios and EWs, we find evidence for the presence of an active galactic nucleus in all sources, including those previously reported as passive. We measure velocity dispersions between 36 and 90km/s, implying the presence of low mass (10^5-6.7^ solar masses) black holes, consistent with literature findings. Finally, we find a significant over-representation (2/5 sources, or a factor of 13^+13^_-10_ quiescent Balmer strong (post-starburst) galaxies among QPE hosts.
638. QPQ VI. HI absorption of z~2 quasars
ID:
ivo://CDS.VizieR/J/ApJ/776/136
Title:
QPQ VI. HI absorption of z~2 quasars
Short Name:
J/ApJ/776/136
Date:
21 Oct 2021
Publisher:
CDS
Description:
With close pairs of quasars at different redshifts, a background quasar sightline can be used to study a foreground quasar's environment in absorption. We use a sample of 650 projected quasar pairs to study the HI Ly{alpha} absorption transverse to luminous, z~2 quasars at proper separations of 30kpc<R_{perp}_<1Mpc. In contrast to measurements along the line-of-sight, regions transverse to quasars exhibit enhanced HI Ly{alpha} absorption and a larger variance than the ambient intergalactic medium, with increasing absorption and variance toward smaller scales. Analysis of composite spectra reveals excess absorption characterized by a Ly{alpha} equivalent width profile W=2.3{AA} (R_{perp}_/100kpc)^-0.46^. We also observe a high (=~60%) covering factor of strong, optically thick HI absorbers (HI column N_HI_>10^17.3^/cm2) at separations R_{perp}_<200kpc, which decreases to ~20% at R_{perp}_=~1Mpc, but still represents a significant excess over the cosmic average. This excess of optically thick absorption can be described by a quasar-absorber cross-correlation function {xi}_QA_(r)=(r/r_0_)^{gamma}^ with a large correlation length r_0_=12.5_-1.4_^+2.7^h^-1^Mpc (comoving) and {gamma}=1.68_-0.30_^+0.14^. The HI absorption measured around quasars exceeds that of any previously studied population, consistent with quasars being hosted by massive dark matter halos M_halo_{approx}10^12.5^M_{sun}_ at z~2.5. The environments of these massive halos are highly biased toward producing optically thick gas, and may even dominate the cosmic abundance of Lyman limit systems and hence the intergalactic opacity to ionizing photons at z~2.5. The anisotropic absorption around quasars implies the transverse direction is much less likely to be illuminated by ionizing radiation than the line-of-sight.
639. QSO 1308+326 at 15GHz modelfit results
ID:
ivo://CDS.VizieR/J/A+A/602/A29
Title:
QSO 1308+326 at 15GHz modelfit results
Short Name:
J/A+A/602/A29
Date:
21 Oct 2021
Publisher:
CDS
Description:
Despite numerous and detailed studies of the jets of Active Galactic Nuclei (AGN) on pc-scales, many questions are still debated. The physical nature of the jet components is one of the most prominent unsolved problems as is the launching mechanism of jets in AGN. The Quasar 1308+326 (z=0.997) allows detailed studies of the overall properties of the jet and to derive a more physical understanding of the nature and origin of jets in general. The long-term data provided by the MOJAVE (Monitoring Of Jets in Active galactic nuclei with VLBA Experiments) survey permit tracing out the structural changes in 1308+326 presented here. The long-lived jet features in this source can be followed for about two decades. We investigate the VLBI morphology and kinematics of the jet of 1308+326 to understand the physical nature of this jet and jets in general, the role of magnetic fields, and the causal connection between jet features and the launching process. 50 VLBA observations performed at 15GHz from the MOJAVE survey have been re-modeled with Gaussian components and re-analyzed (the time covered: 1995.05-2014.07). The analysis is supplemented by multi-wavelength radio-data (UMRAO, at 4.8, 8.0, and 14.5GHz) in polarization and total intensity. We fit the apparent motion of the jet features with the help of a model of a precessing nozzle. The jet features seem to be emitted with varying viewing angles and launched into an ejection cone. Tracing the component paths yields evidence for rotational motion. Radio flux-density variability can be explained as a consequence of enhanced Doppler boosting corresponding to the motion of the jet relative to the line of sight. Based on the presented kinematics and other indicators, such as electric-vector polarization position angle (EVPA)-rotation we conclude that the jet of 1308+326 has a helical structure, i.e. the components are moving along helical trajectories, while the trajectories themselves are experiencing a precessing motion as well. A model of a precessing nozzle (Qian et al., 2014RAA....14..249Q) was applied to the data and a subset of the observed jet feature paths can be modeled successfully within this model. The data through 2012 are consistent with a swing period of 16.9 years. We discuss several scenarios to explain the observed motion phenomena, including a binary black hole model. It seems unlikely that the accretion disk around the primary black hole, that is disturbed by tidal forces of the secondary black hole, is able to launch a persistent axisymmetric jet. We conclude that we are observing a rotating helix. In particular, the observed EVPA swings can be explained by a shock moving through a straight jet pervaded by a helical magnetic field. We compare our results for 1308+326 with other astrophysical scenarios where similar, wound up filamentary structures are found. They all are related to accretion-driven processes. A helically moving or wound up object is often explained by filamentary features moving along magnetic field lines of magnetic flux tubes. It seems that a "component" is plasma tracing the magnetic field which guides the motion of the radiating radio-band plasma. Further investigations and modeling are in preparation.
640. QSO B0218+357 molecular absorption lines
ID:
ivo://CDS.VizieR/J/A+A/595/A96
Title:
QSO B0218+357 molecular absorption lines
Short Name:
J/A+A/595/A96
Date:
21 Oct 2021
Publisher:
CDS
Description:
Isotopic ratios of heavy elements are a key signature of the nucleosynthesis processes in stellar interiors. The contribution of successive generations of stars to the metal enrichment of the Universe is imprinted on the evolution of isotopic ratios over time. We investigate the isotopic ratios of carbon, nitrogen, oxygen, and sulfur through millimeter molecular absorption lines arising in the z=0.68 absorber toward the blazar B 0218+357. We find that these ratios differ from those observed in the Galactic interstellar medium, but are remarkably close to those in the only other source at intermediate redshift for which isotopic ratios have been measured to date, the z=0.89 absorber in front of PKS 1830-211. The isotopic ratios in these two absorbers should reflect enrichment mostly from massive stars, and they are indeed close to the values observed toward local starburst galaxies. Our measurements set constraints on nucleosynthesis and chemical evolution models.