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741. Stellar Catalogue in the Chandra DFS
ID:
ivo://CDS.VizieR/J/A+A/392/741
Title:
Stellar Catalogue in the Chandra DFS
Short Name:
J/A+A/392/741
Date:
21 Oct 2021
Publisher:
CDS
Description:
Stellar catalogues in five passbands (UBVRI) over an area of approximately 0.3{deg}^2^, comprising about 1200 objects, and in seven passbands (UBVRIJK) over approximately 0.1{deg}^2^, comprising about 400 objects, in the direction of the Chandra Deep Field South are presented. The 90% completeness level of the number counts is reached at approximately U=23.8, B=24.0, V=23.5, R=23.0, I=21.0, J=20.5, K=19.0. These multi-band catalogues have been produced from publicly available, single passband catalogues. A scheme is presented to select point sources from these catalogues, by combining the SExtractor parameter CLASS_STAR from all available passbands. Probable QSOs and unresolved galaxies are identified by using the previously developed {chi}^2^-technique (Hatziminaoglou et al., 2002, Cat. <J/A+A/384/81>), that fits the overall spectral energy distributions to template spectra and determines the best fitting template. Approximately 15% of true galaxies are misclassified as stars by the {chi}^2^ method. The number of unresolved galaxies and QSOs identified by the {chi}^2^-technique, allows us to estimate that the remaining level of contamination by such objects is at the level of 2.4% of the number of stars. The fraction of missing stars being incorrectly removed as QSOs or unresolved galaxies is estimated to be similar. The resulting stellar catalogues and the objects identified as likely QSOs and unresolved galaxies with coordinates, observed magnitudes with errors and assigned spectral types by the {chi}^2^-technique are presented and are publicly available.
742. Stellar masses of optical & IR QSO hosts
ID:
ivo://CDS.VizieR/J/ApJ/819/L27
Title:
Stellar masses of optical & IR QSO hosts
Short Name:
J/ApJ/819/L27
Date:
21 Oct 2021
Publisher:
CDS
Description:
The relation between star formation rates (SFRs) and stellar masses, i.e., the galaxy main sequence, is a useful diagnostic of galaxy evolution. We present the distributions relative to the main sequence of 55 optically selected PG and 12 near-IR-selected Two Micron All Sky Survey (2MASS) quasars at z<=0.5. We estimate the quasar host stellar masses from Hubble Space Telescope or ground-based AO photometry, and the SFRs through the mid-infrared aromatic features and far-IR photometry. We find that PG quasar hosts more or less follow the main sequence defined by normal star-forming galaxies while 2MASS quasar hosts lie systematically above the main sequence. PG and 2MASS quasars with higher nuclear luminosities seem to have higher specific SFRs (sSFRs), although there is a large scatter. No trends are seen between sSFRs and SMBH masses, Eddington ratios, or even morphology types (ellipticals, spirals, and mergers). Our results could be placed in an evolutionary scenario with quasars emerging during the transition from ULIRGs/mergers to ellipticals. However, combined with results at higher redshift, they suggest that quasars can be widely triggered in normal galaxies as long as they contain abundant gas and have ongoing star formation.
743. Strong MgII absorber blazars
ID:
ivo://CDS.VizieR/J/MNRAS/473/5154
Title:
Strong MgII absorber blazars
Short Name:
J/MNRAS/473/5154
Date:
21 Oct 2021
Publisher:
CDS
Description:
It is widely believed that the cool gas clouds traced by MgII absorption, within a velocity offset of 5000km/s relative to the background quasar are mostly associated with the quasar itself, whereas the absorbers seen at larger velocity offsets towards us are intervening absorber systems and hence their existence is completely independent of the background quasar. Recent evidence by Bergeron et al. (2011A&A...525A..61P, hereinafter BBM) has seriously questioned this paradigm, by showing that the number density of intervening MgII absorbers towards the 45 blazars in their sample is nearly two times the expectation based on the MgII absorption systems seen towards normal quasars (QSOs). Given its serious implications, it becomes important to revisit this finding, by enlarging the blazar sample and subjecting it to an independent analysis. Here, we first report the outcome of our re-analysis of the available spectroscopic data for the BBM sample itself. Our analysis of the BBM sample reproduces their claimed factor of 2 excess of dN/dz along blazar sightlines, vis-a-vis normal QSOs. We have also assembled an approximately three times larger sample of blazars, albeit with moderately sensitive optical spectra. Using this sample together with the BBM sample, our analysis shows that the dN/dz of the MgII absorbers statistically matches that known for normal QSO sightlines. Further, the analysis indicates that associated absorbers might be contributing significantly to the estimated dN/dz up to offset speeds {DELTA}v~0.2c relative to the blazar.
744. Subaru H images of UM673
ID:
ivo://CDS.VizieR/J/A+A/566/A36
Title:
Subaru H images of UM673
Short Name:
J/A+A/566/A36
Date:
21 Oct 2021
Publisher:
CDS
Description:
We performed a detailed photometric analysis of the lensed system UM673 (Q0142-100) and an analysis of the tentative lens models. High-resolution adaptive optics images of UM673 taken with the Subaru telescope in the H band were examined. We also analysed the J, H and K-band observational data of UM673 obtained with the 1.3m telescope at the CTIO observatory. We present photometry of quasar components A and B of UM673, the lens, and the nearby bright galaxy using H-band observational data obtained with the Subaru telescope. Based on the CTIO observations of UM673, we also present J- and H-band photometry and estimates of the J, H and K-band flux ratios between the two UM673 components in recent epochs. The near-infrared fluxes of the A and B components of UM673 and their published optical fluxes are analysed to measure extinction properties of the lensing galaxy. We estimate the extinction-corrected flux ratio between components A and B to be about 2.14 mag. We discuss lens models for the UM673 system constrained with the positions of the UM673 components, their flux ratio, and the previously measured time delay.
745. Superluminal motion in AGN
ID:
ivo://CDS.VizieR/J/other/ChJAA/8.385
Title:
Superluminal motion in AGN
Short Name:
J/other/ChJAA/8.
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have collected an up-to-date sample of 123 superluminal sources (84 quasars, 27 BL Lac objects and 12 galaxies) and calculated the apparent velocities ({beta}_app_) for 224 components in the sources with the {Lambda}-CDM model. We checked the relationships between their proper motions, redshifts, {beta}_app_ and 5GHz flux densities. Our analysis shows that the radio emission is strongly boosted by the Doppler effect. The superluminal motion and the relativistic beaming boosting effect are, to some extent, the same in active galactic nuclei.
746. Survey of low-redshift OVI absorbers
ID:
ivo://CDS.VizieR/J/ApJS/177/39
Title:
Survey of low-redshift OVI absorbers
Short Name:
J/ApJS/177/39
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using high-resolution ultraviolet spectra of 16 low-z QSOs obtained with the E140M echelle mode of the Space Telescope Imaging Spectrograph, we study the physical conditions and statistics of OVI absorption in the intergalactic medium (IGM) at z<0.5. We identify 51 intervening (z_abs_<z_QSO_) OVI systems comprising 77 individual components, and we find 14 "proximate" systems (z_abs_~z_QSO_) containing 34 components. For intervening systems (components) with rest-frame equivalent width W_r_>30m{AA}, the number of OVI absorbers per unit redshift dN/dz=15.6^+2.9^_-2.4_(21.0^+3.2^_-2.8_), and this decreases to dN/dz=0.9^+1.0^_-0.5_(0.3^+0.7^_-0.3_) for W_r_>300m{AA}. The number per redshift increases steeply as z_abs_ approaches z_QSO_; we find that dN/dz is ~3-10 times higher within 2500km/s of z_QSO_. The most striking difference between intervening and proximate systems is that some proximate absorbers have substantially lower HI/OVI ratios.
747. Survey of optically variables QSOs
ID:
ivo://CDS.VizieR/J/A+A/296/665
Title:
Survey of optically variables QSOs
Short Name:
J/A+A/296/665
Date:
21 Oct 2021
Publisher:
CDS
Description:
We describe a survey for variable QSOs carried out for 15 years with the UK Schmidt telescope, using IIIaJ plates exposed behind a Schott GG395 filter. Objects brighter than B=21.0 on a reference plate and displaying a peak to peak amplitude of variability larger than B=0.35mag are selected. Plates in U, V, R and I were also obtained.
748. SWIRE/SDSS quasars
ID:
ivo://CDS.VizieR/J/MNRAS/386/1252
Title:
SWIRE/SDSS quasars
Short Name:
J/MNRAS/386/1252
Date:
21 Oct 2021
Publisher:
CDS
Description:
We derive the properties of dusty tori in active galactic nuclei from the comparison of observed spectral energy distributions (SEDs) of SDSS quasars and a precomputed grid of torus models. The observed SEDs comprise SDSS photometry, Two-Micron All-Sky Survey J, H and K data, whenever available, and mid-infrared (mid-IR) data from the Spitzer Wide-area InfraRed Extragalactic Survey.
749. SWIRE/SDSS quasars. II. Type 2 AGN
ID:
ivo://CDS.VizieR/J/MNRAS/399/1206
Title:
SWIRE/SDSS quasars. II. Type 2 AGN
Short Name:
J/MNRAS/399/1206
Date:
21 Oct 2021
Publisher:
CDS
Description:
This paper is the second part of a work investigating the properties of dusty tori in active galactic nuclei (AGN) by means of multicomponent spectral energy distribution (SED) fitting. It focuses on low-luminosity, low-redshift (z<=0.25) AGN selected among emission line galaxies in the overlapping regions between Spitzer Wide-area Infrared Extragalactic Survey (SWIRE) and Sloan Digital Sky Survey Data Release 4 as well as X-ray, radio and mid-infrared selected type 2 AGN samples from the literature. The available multiband photometry covers the spectral range from the u band up to 160um. Using a standard chi^2^ minimization, the observed SED of each object is fit to a set of multicomponent models comprising a stellar component, a high optical depth (tau_9.7_>=1.0) torus and cold emission from a starburst (SB). The torus components assigned to the majority of the objects were those of the highest optical depth of our grid of models (tau_9.7_=10.0). The contribution of the various components (stars, torus, SB) is reflected in the position of the objects on the Infrared Array Camera (IRAC) colour diagram, with star-, torus- and SB-dominated objects occupying specific areas of the diagrams and composite objects lying in between.
750. Synchrotron peak frequency of 135 AGN
ID:
ivo://CDS.VizieR/J/A+A/488/867
Title:
Synchrotron peak frequency of 135 AGN
Short Name:
J/A+A/488/867
Date:
21 Oct 2021
Publisher:
CDS
Description:
The blazar sequence is a scenario in which the bolometric luminosity of the blazar governs the appearance of its spectral energy distribution. The most prominent result is the significant negative correlation between the synchrotron peak frequencies and the synchrotron peak luminosities of the blazar population. Observational studies of the blazar sequence have, in general, neglected the effect of Doppler boosting. We study the dependence of both the synchrotron peak frequency and luminosity with Doppler-corrected quantities. We determine the spectral energy distributions of 135 radio-bright AGN and find the best-fit parabolic function for the distribution to quantify their synchrotron emission. The corresponding measurements of synchrotron peak luminosities and frequencies are Doppler-corrected with a new set of Doppler factors calculated from variability data. The relevant correlations for the blazar sequence are determined for these intrinsic quantities.