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671. Quadruply lensed quasar WFI2033-4723 light curves
ID:
ivo://CDS.VizieR/J/A+A/629/A97
Title:
Quadruply lensed quasar WFI2033-4723 light curves
Short Name:
J/A+A/629/A97
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new measurements of the time delays of WFI2033-4723. The data sets used in this work include 14 years of data taken at the 1.2m Leonhard Euler Swiss telescope, 13 years of data from the SMARTS 1.3m telescope at Las Campanas Observatory and a single year of high-cadence and high-precision monitoring at the MPIA 2.2m telescope. The time delays measured from these different data sets, all taken in the R-band, are in good agreement with each other and with previous measurements from the literature. Combining all the time-delay estimates from our data sets results in Dt_AB_=36.2_-0.8_^+0.7^days (2.1% precision), Dt_AC_=-23.3_-1.4_^+1.2^days (5.6%) and Dt_BC_=-59.4_-1.3_^+1.3^days (2.2%). In addition, the close image pair A1-A2 of the lensed quasars can be resolved in the MPIA 2.2m data. We measure a time delay consistent with zero in this pair of images. We also explore the prior distributions of microlensing time-delay potentially affecting the cosmological time-delay measurements of WFI2033-4723. There is however no strong indication in our measurements that microlensing time delay is neither present nor absent. This work is part of a H0LiCOW series focusing on measuring the Hubble constant from WFI2033-4723.
672. Quasar absorption-line systems
ID:
ivo://CDS.VizieR/J/AJ/112/62
Title:
Quasar absorption-line systems
Short Name:
J/AJ/112/62
Date:
21 Oct 2021
Publisher:
CDS
Description:
A survey of quasar absorbers was conducted using the Infrared Astronomical Satellite (IRAS) database. Quasars with known intervening absorption-line systems and broad absorption line (BAL) QSOs were selected primarily from Junkkarinen et al. (1991ApJS...77..203J). Of the 570 quasars with IRAS data, 52 showed 3{sigma} or better detections in at least one band in SCANPI analysis. The origin of the IRAS flux could be from the absorption-line systems, other galaxies, or the quasar itself. The spectral energy distributions for quasars detected in the absorption-line sample and BAL QSOs were found to be redder than those of two control samples which suggests that some of the IRAS flux may arise in dust associated with the intervening galaxies. IRAS SUPERSCANPI processing was carried out for 77 quasars with known MgII absorption at Zabs<1 to investigate the ensemble far-infrared properties of these objects. SUPERSCANPI processing evaluates the median flux for many different positions on the sky, resulting in an improvement in the effective sensitivity. A control sample consisting of objects with no MgII absorption known at Zabs<1 but with the same distribution of absolute V-magnitude, Zem and radio-loud fraction for the background quasars was also processed. The MgII sample was detected at 3{sigma} or better in all four IRAS bands with a significantly larger flux than the control sample at 60{mu}m and 100{mu}m. If this far-infrared emission is from the absorber galaxies, then the far-infrared luminosity of the composite MgII absorber was found to be comparable to that of a starbursting galaxy, although such a high star-formation rate is inconsistent with the optical and near-infrared colors of low-redshift MgII systems. Four of the quasars with individual IRAS detections have intervening galaxies identified with the MgII absorption-lines. The spectral energy distributions of these galaxies imply far-infrared luminosities in excess of what Arp 220 would give at their redshifts. While all the external evidence suggests that the detection of far-infrared emission from the absorber sample may not be connected to the presence of the MgII absorber, we discuss future observations which may help explain our results.
673. Quasar and radio galaxies flux densities
ID:
ivo://CDS.VizieR/J/A+A/319/757
Title:
Quasar and radio galaxies flux densities
Short Name:
J/A+A/319/757
Date:
21 Oct 2021
Publisher:
CDS
Description:
The tables described below contain the data used in the analysis. The data have been taken from various sources in the literature. The references to the data can be found in the paper. Table 1 contains the data of the 3C radio galaxy sample. Table 2 contains the data of the 3C quasar sample. Table 3 contains the data of the 4C quasar sample. The tables list the name of the object, its redshift, the value of the Q-parameter (ratio between the core and extended flux at 5 GHz observed frequency), and the flux densities at various frequencies.
674. Quasar black hole masses
ID:
ivo://CDS.VizieR/J/ApJ/669/791
Title:
Quasar black hole masses
Short Name:
J/ApJ/669/791
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate the time-dependent variations of ultraviolet (UV) black hole mass estimates of quasars in the Sloan Digital Sky Survey (SDSS). From SDSS spectra of 615 high-redshift (1.69<z<4.75) quasars with spectra from two epochs, we estimate black hole masses using a single-epoch technique, which employs an additional, automated night-sky line removal and relies on UV continuum luminosity and CIV {lambda}1549 emission-line dispersion. Mass estimates show variations between epochs at about the 30% level for the sample as a whole. We determine that for our full sample, measurement error in the line dispersion likely plays a larger role than the inherent variability in terms of contributing to variations in mass estimates between epochs. However, we use the variations in quasars with r-band spectral signal-to-noise ratio greater than 15 to estimate that the contribution to these variations from inherent variability is roughly 20%. We conclude that these differences in black hole mass estimates between epochs indicate that variability does not make a large contribution to the current factor of 2 scatter between mass estimates derived from low- and high-ionization emission lines.
675. Quasar Candidates
ID:
ivo://CDS.VizieR/VII/143
Title:
Quasar Candidates
Short Name:
VII/143
Date:
21 Oct 2021
Publisher:
CDS
Description:
This data set is based on data in three publications. The positions and magnitudes of quasar candidates discovered on Canada-France Hawaii-Telescope (CFHT) blue green plates are given. Spectroscopy with the Multiple Mirror Telescope (MMT) indicates that 70 percent of the candidates are quasars, and most of the others are white dwarfs or hot subluminous stars. Most of the redshifts are less than z=1.7. Additional spectroscopic observations at Steward Observatory were used. The catalog lists a name based on position, B1950 position, B magnitude, or visual magnitude, redshift, and remarks.
676. Quasar candidates selected from the SDSS
ID:
ivo://CDS.VizieR/J/AJ/137/3884
Title:
Quasar candidates selected from the SDSS
Short Name:
J/AJ/137/3884
Date:
21 Oct 2021
Publisher:
CDS
Description:
We explore the multidimensional, multiwavelength selection of quasars from mid-infrared (MIR) plus optical data, specifically from Spitzer-Infrared Array Camera (IRAC) and the Sloan Digital Sky Survey (SDSS). Traditionally, quasar selection relies on cuts in two-dimensional color space despite the fact that most modern surveys (optical and IR) are done in more than three bandpasses. In this paper, we apply modern statistical techniques to combined Spitzer MIR and SDSS optical data, allowing up to eight-dimensional (8-D) color selection of quasars. Using a Bayesian selection method, we catalog 5546 quasar candidates to an 8.0{mu}m depth of 56{mu}Jy over an area of ~24{deg}^2^. Roughly 70% of these candidates are not identified by applying the same Bayesian algorithm to 4-color SDSS optical data alone. The 8-D optical+MIR selection on this data set recovers 97.7% of known type 1 quasars in this area and greatly improves the effectiveness of identifying 3.5<z<5 quasars which are challenging to identify (without considerable contamination) using MIR data alone.
677. Quasar 3C 345 at 18 cm with RadioAstron
ID:
ivo://CDS.VizieR/J/A+A/648/A82
Title:
Quasar 3C 345 at 18 cm with RadioAstron
Short Name:
J/A+A/648/A82
Date:
23 Mar 2022 16:32:52
Publisher:
CDS
Description:
Supermassive black holes in the centres of radio-loud active galactic nuclei (AGN) can produce collimated relativistic outflows (jets). Magnetic fields are thought to play a key role in the formation and collimation of these jets, but the details are much debated. We study the innermost jet morphology and magnetic field strength in the AGN 3C 345 with an unprecedented resolution using images obtained within the framework of the key science programme on AGN polarisation of the Space VLBI mission RadioAstron. We observed the flat spectrum radio quasar 3C 345 at 1.6GHz on 2016 March 30 with RadioAstron and 18 ground-based radio telescopes in full polarisation mode. Our images, in both total intensity and linear polarisation, reveal a complex jet structure at 300{mu}as as angular resolution, corresponding to a projected linear scale of about 2pc or a few thousand gravitational radii. We identify the synchrotron self-absorbed core at the jet base and find the brightest feature in the jet 1.5 mas downstream of the core. Several polarised components appear in the Space VLBI images that cannot be seen from ground array-only images. Except for the core, the electric vector position angles follow the local jet direction, suggesting a magnetic field perpendicular to the jet. This indicates the presence of plane perpendicular shocks in these regions. Additionally, we infer a minimum brightness temperature at the largest uv-distances of 1.1x10^12^K in the source frame, which is above the inverse Compton limit and an order of magnitude larger than the equipartition value. This indicates locally efficient injection or re-acceleration of particles in the jet to counter the inverse Compton cooling or the geometry of the jet creates significant changes in the Doppler factor, which has to be >11 to explain the high brightness temperatures.
678. Quasar composite made from bright QSOs
ID:
ivo://CDS.VizieR/J/A+A/585/A87
Title:
Quasar composite made from bright QSOs
Short Name:
J/A+A/585/A87
Date:
21 Oct 2021
Publisher:
CDS
Description:
Quasi-stellar object (QSO) spectral templates are important both to QSO physics and for investigations that use QSOs as probes of intervening gas and dust. However, combinations of various QSO samples obtained at different times and with different instruments so as to expand a composite and to cover a wider rest frame wavelength region may create systematic effects, and the contribution from QSO hosts may contaminate the composite. We have constructed a composite spectrum from luminous blue QSOs at 1<z<2.1 selected from the Sloan Digital Sky Survey (SDSS). The observations with X-shooter simultaneously cover ultraviolet (UV) to near-infrared (NIR) light, which ensures that the composite spectrum covers the full rest-frame range from Ly{beta} to 11350{AA} without any significant host contamination. Assuming a power-law continuum for the composite we find a spectral slope of {alpha}{lambda}=1.70+/-0.01, which is steeper than previously found in the literature. We attribute the differences to our broader spectral wavelength coverage, which allows us to effectively avoid fitting any regions that are affected either by strong QSO emissions lines (e.g., Balmer lines and complex [FeII] blends) or by intrinsic host galaxy emission. Finally, we demonstrate the application of the QSO composite spectrum for evaluating the reddening in other QSOs.
679. Quasar evolution
ID:
ivo://CDS.VizieR/J/ApJ/269/352
Title:
Quasar evolution
Short Name:
J/ApJ/269/352
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the Bright Quasar Survey (BQS) consisting of 114 objects to an average limiting magnitude B=16.16 over an area of 10714{deg}^2^. There are 92 quasars with M_B_<-23 in the sample. We use the BQS and complete samples from published surveys to derive models of the statistical evolution of quasars. The increase of space density with redshift depends strongly on absolute luminosity, being close to zero for low-luminosity quasars. Detailed predictions are given for the distribution of redshifts and magnitudes and for the total counts based on the evolution models.
680. Quasar from SDSS and UKIDSS
ID:
ivo://CDS.VizieR/J/MNRAS/406/1583
Title:
Quasar from SDSS and UKIDSS
Short Name:
J/MNRAS/406/1583
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a sample of 8498 quasars with both Sloan Digital Sky Survey (SDSS) ugriz optical and United Kingdom Infrared Telescope (UKIRT) Infrared Deep Sky Survey (UKIDSS) YJHK near-infrared (near-IR) photometric data. With this sample, we obtain the median colour-z relations based on 7400 quasars with magnitude uncertainties less than 0.1mag in all bands. By analysing the quasar colours, we propose an empirical criterion in the Y-K versus g-z colour-colour diagram to separate stars and quasars with redshift z<4, and two other criteria for selecting high-redshift quasars. Using the SDSS-UKIDSS colour-z relations, we estimate the photometric redshifts of 8498 SDSS-UKIDSS quasars, and find that 85.0 per cent of them are consistent with the spectroscopic redshifts within |{Delta}z|<0.2, which leads to a significant increase of the photometric redshift accuracy from that based on the SDSS colour-z relations only. As two tests, we compare our colour-selection criterion with a small UKIDSS/EDR quasar/star sample and a sample of 4671 variable sources in the SDSS Stripe 82 region with both SDSS and UKIDSS data. We find that they can be clearly divided into two classes (quasars and stars) by our criterion in the Y-K versus g-z plot.