- ID:
- ivo://CDS.VizieR/J/AJ/149/203
- Title:
- Reddening of ~35000 quasars from SDSS
- Short Name:
- J/AJ/149/203
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the extinction/reddening of ~35000 uniformly selected quasars with 0<z{<=}5.3 in order to better understand their intrinsic optical/ultraviolet (UV) spectral energy distributions. Using rest-frame optical-UV photometry taken from the Sloan Digital Sky Survey's (SDSS) 7th data release, cross-matched to WISE in the mid-infrared, 2MASS and UKIDSS in the near-infrared, and GALEX in the UV, we isolate outliers in the color distribution and find them well described by an SMC-like reddening law. A hierarchical Bayesian model with a Markov Chain Monte Carlo sampling method was used to find distributions of power law indices and E(B-V) consistent with both the broad absorption line (BAL) and non-BAL samples. We find that, of the ugriz color-selected type 1 quasars in SDSS, 2.5% (13%) of the non-BAL (BAL) sample are consistent with E(B-V)>0.1 and 0.1% (1.3%) with E(B-V)>0.2. Simulations show both populations of quasars are intrinsically bluer than the mean composite, with a mean spectral index ({alpha}_{lambda}_) of -1.79 (-1.83). The emission and absorption-line properties of both samples reveal that quasars with intrinsically red continua have narrower Balmer lines and stronger high-ionization emission lines, the latter indicating a harder continuum in the extreme-UV and the former pointing to differences in black hole mass and/or orientation.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/470/4838
- Title:
- Redshift catalog of HE 0435-1223 field-of-view
- Short Name:
- J/MNRAS/470/4838
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Galaxies located in the environment or along the line of sight towards gravitational lenses can significantly affect lensing observables, and can lead to systematic errors on the measurement of H_0_ from the time-delay technique. We present the results of a systematic spectroscopic identification of the galaxies in the field of view of the lensed quasar HE 0435-1223 using the W.M. Keck, Gemini and ESO-Very Large telescopes. Our new catalogue triples the number of known galaxy redshifts in the direct vicinity of the lens, expanding to 102 the number of measured redshifts for galaxies separated by less than 3 arcmin from the lens. We complement our catalogue with literature data to gather redshifts up to 15 arcmin from the lens, and search for galaxy groups or clusters projected towards HE 0435-1223. We confirm that the lens is a member of a small group that includes at least 12 galaxies, and find 8 other group candidates near the line of sight of the lens. The flexion shift, namely the shift of lensed images produced by high-order perturbation of the lens potential, is calculated for each galaxy/group and used to identify which objects produce the largest perturbation of the lens potential. This analysis demonstrates that (i) at most three of the five brightest galaxies projected within 12 arcsec of the lens need to be explicitly used in the lens models, and (ii) the groups can be treated in the lens model as an external tidal field (shear) contribution.
- ID:
- ivo://CDS.VizieR/J/MNRAS/410/860
- Title:
- Redshift dependence of BAL QSOs
- Short Name:
- J/MNRAS/410/860
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe the application of non-negative matrix factorization to generate compact reconstructions of quasar spectra from the Sloan Digital Sky Survey (SDSS), with particular reference to broad absorption line quasars (BALQSOs). BAL properties are measured for SiIV{lambda}1400, CIV{lambda}1550, AlIII{lambda}1860 and MgII{lambda}2800, resulting in a catalogue of 3547 BALQSOs. Two corrections, based on extensive testing of synthetic BALQSO spectra, are applied in order to estimate the intrinsic fraction of CIV BALQSOs. First, the probability of an observed BALQSO spectrum being identified as such by our algorithm is calculated as a function of redshift, signal-to-noise ratio and BAL properties. Secondly, the different completenesses of the SDSS target selection algorithm for BALQSOs and non-BAL quasars are quantified.
- ID:
- ivo://CDS.VizieR/J/A+A/434/475
- Title:
- Redshifts for X-ray selected AGNs
- Short Name:
- J/A+A/434/475
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present photometric redshift estimates for X-ray selected sources detected in the XMM/2dF survey. 5-band photometry for 193 sources has been obtained from the SDSS. We exclude 10 sources associated with Galactic stars. The tabulated data include the optical coordinate of all sources in our sample, their photometric redshift estimate, their r-band magnitude and g-r colour as well as their morphological classification (these optical parameters have been used in the discussion of our results). Spectroscopic redshifts are available only for a sub-sample of our data and are included in Table 1 together with the survey from which they have been obtained.
- ID:
- ivo://CDS.VizieR/J/AJ/131/2788
- Title:
- Redshifts in the SFQS survey
- Short Name:
- J/AJ/131/2788
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we present the first results of a deep spectroscopic survey of faint quasars in the Sloan Digital Sky Survey (SDSS) Southern Survey, a deep survey carried out by repeatedly imaging a 270{deg}^2^ area. Quasar candidates were selected from the deep data with good completeness over 0<z<5 and 2-3mag fainter than the SDSS main survey. Spectroscopic follow-up was carried out on the 6.5m MMT with Hectospec. The preliminary sample of this SDSS faint quasar survey (SFQS) covers ~3.9{deg}^2^, contains 414 quasars, and reaches g=22.5.
- ID:
- ivo://CDS.VizieR/J/MNRAS/346/1103
- Title:
- Redshifts of damped Lyman{alpha} absorbers
- Short Name:
- J/MNRAS/346/1103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the evolution of the column density distribution, f(N,z), and total neutral hydrogen mass in high column density quasar absorbers using candidates from a recent high-redshift survey for damped Lyman{alpha} (DLA) and Lyman-limit system (LLS) absorbers.
- ID:
- ivo://CDS.VizieR/J/MNRAS/367/1261
- Title:
- Redshift survey in 15 quasar fields
- Short Name:
- J/MNRAS/367/1261
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the relative distribution of the gaseous contents of the Universe (as traced by a sample of Ly{alpha} absorbers), and the luminous baryonic matter (as traced by a redshift survey of galaxies in the same volume searched for Ly{alpha} absorbers), along 16 lines of sight (LOS) between redshifts 0 and 1. Our galaxy redshift survey was made with the multi-object spectrograph on the Canada-France-Hawaii Telescope and, when combined with galaxies from the literature in the same LOS, gives us a galaxy sample of 636 objects. By combining this with an absorption-line sample of 406 absorbing systems drawn from published works, we are able to study the relationship between gas and galaxies over the latter half of the age of the Universe.
- ID:
- ivo://CDS.VizieR/J/other/Sci/338.1445
- Title:
- Relativistic jets from black hole systems
- Short Name:
- J/other/Sci/338.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Black holes generate collimated, relativistic jets, which have been observed in {gamma}-ray bursts (GRBs), microquasars, and at the center of some galaxies [active galactic nuclei (AGN)]. How jet physics scales from stellar black holes in GRBs to the supermassive ones in AGN is still unknown. Here, we show that jets produced by AGN and GRBs exhibit the same correlation between the kinetic power carried by accelerated particles and the {gamma}-ray luminosity, with AGN and GRBs lying at the low- and high-luminosity ends, respectively, of the correlation. This result implies that the efficiency of energy dissipation in jets produced in black hole systems is similar over 10 orders of magnitude in jet power, establishing a physical analogy between AGN and GRBs.
- ID:
- ivo://CDS.VizieR/J/AJ/133/2357
- Title:
- Relativistic jets in the RRFID database
- Short Name:
- J/AJ/133/2357
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of an analysis of relativistic jet apparent speeds from VLBI images in the Radio Reference Frame Image Database (RRFID). The images are snapshot VLBI images at 8 and 2GHz using the VLBA, plus up to 10 additional antennas that provide global VLBI coverage. We have analyzed the 8GHz images from the first 5 years of the database (1994-1998), for all sources observed at three or more epochs during this time range. This subset comprises 966 images of 87 sources. The sources in this subset have an average of 11 epochs of observation over the years 1994-1998, with the best-observed sources having 19 epochs. About half of the sources in this RRFID kinematic survey have not been previously studied with multi-epoch VLBI observations. We have measured apparent speeds for a total of 184 jet components in 77 sources, of which the best-measured 94 component speeds in 54 sources are used in the final analysis.
- ID:
- ivo://CDS.VizieR/J/ApJ/758/84
- Title:
- Relativistic jets in the RRFID database. II. 10yr
- Short Name:
- J/ApJ/758/84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze blazar jet apparent speeds and accelerations from the RDV series of astrometric and geodetic very long baseline interferometry (VLBI) experiments. From these experiments, we have produced and analyzed 2753 global VLBI images of 68 sources at 8GHz with a median beam size of 0.9 milliarcseconds (mas) and a median of 43 epochs per source. From this sample, we analyze the motions of 225 jet components in 66 sources. The distribution of the fastest measured apparent speed in each source has a median of 8.3c and a maximum of 44c. Sources in the 2FGL Fermi LAT catalog display higher apparent speeds than those that have not been detected. On average, components farther from the core in a given source have significantly higher apparent speeds than components closer to the core; for example, for a typical source, components at ~3mas from the core (~15pc projected at z~0.5) have apparent speeds about 50% higher than those of components at ~1mas from the core (~5pc projected at z~0.5). We measure accelerations of components in orthogonal directions parallel and perpendicular to their average velocity vector. Parallel accelerations have significantly larger magnitudes than perpendicular accelerations, implying that observed accelerations are predominantly due to changes in the Lorentz factor (bulk or pattern) rather than projection effects from jet bending. Positive parallel accelerations are significantly more common than negative ones, so the Lorentz factor (bulk or pattern) tends to increase on the scales observed here. Observed parallel accelerations correspond to modest source frame increases in the bulk or pattern Lorentz factor.
