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Start Over Subject quasars Content Level Research
51. 3.5 and 1.3mm polarimetric survey of Northern AGNs
ID:
ivo://CDS.VizieR/J/A+A/566/A59
Title:
3.5 and 1.3mm polarimetric survey of Northern AGNs
Short Name:
J/A+A/566/A59
Date:
21 Oct 2021
Publisher:
CDS
Description:
Short millimeter observations of radio-loud active galactic nuclei (AGN) offer an excellent opportunity to study the physics of their synchrotron-emitting relativistic jets from where the bulk of radio and millimeter emission is radiated. On one hand, AGN jets and their emission cores are significantly less affected by Faraday rotation and depolarization than at longer wavelengths. On the other hand, the millimeter emission of AGN is dominated by the compact innermost regions in the jets, where the jet cannot be seen at longer wavelengths due to synchrotron opacity. We present the first simultaneous dual frequency 86GHz and 229GHz polarimetric survey of all four Stokes parameters for a large sample of 211 radio-loud active galactic nuclei, designed to be flux limited at 1Jy at 86GHz. Most of the observations were made in mid-August 2010 using the XPOL polarimeter on the IRAM 30m millimetric radio telescope.
52. A new photo-z method for quasars in Stripe 82
ID:
ivo://CDS.VizieR/J/AJ/154/269
Title:
A new photo-z method for quasars in Stripe 82
Short Name:
J/AJ/154/269
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a new algorithm to estimate quasar photometric redshifts (photo-zs), by considering the asymmetries in the relative flux distributions of quasars. The relative flux models are built with multivariate Skew-t distributions in the multidimensional space of relative fluxes as a function of redshift and magnitude. For 151392 quasars in the SDSS, we achieve a photo-z accuracy, defined as the fraction of quasars with the difference between the photo-z z_p_ and the spectroscopic redshift z_s_, |{Delta}_z_|=|z_s_-z_p_|/(1+z_s_) within 0.1, of 74%. Combining the WISE W1 and W2 infrared data with the SDSS data, the photo-z accuracy is enhanced to 87%. Using the Pan-STARRS1 or DECaLS photometry with WISE W1 and W2 data, the photo-z accuracies are 79% and 72%, respectively. The prior probabilities as a function of magnitude for quasars, stars, and galaxies are calculated, respectively, based on (1) the quasar luminosity function, (2) the Milky Way synthetic simulation with the Besancon model, and (3) the Bayesian Galaxy Photometric Redshift estimation. The relative fluxes of stars are obtained with the Padova isochrones, and the relative fluxes of galaxies are modeled through galaxy templates. We test our classification method to select quasars using the DECaLS g, r, z, and WISE W1 and W2 photometry. The quasar selection completeness is higher than 70% for a wide redshift range 0.5<z<4.5, and a wide magnitude range 18<r<21.5 mag. Our photo-z regression and classification method has the potential to extend to future surveys. The photo-z code will be publicly available.
53. An optical overview of blazars with LAMOST. I.
ID:
ivo://CDS.VizieR/J/AJ/161/196
Title:
An optical overview of blazars with LAMOST. I.
Short Name:
J/AJ/161/196
Date:
16 Mar 2022 11:51:00
Publisher:
CDS
Description:
The extragalactic {gamma}-rays sky observed by the Fermi Large Area Telescope (LAT) is dominated by blazars. In the fourth release of the Fermi LAT Point Source Catalog (4FGL) are sources showing a multifrequency behavior similar to that of blazars but lacking an optical spectroscopic confirmation of their nature, known as blazar candidates of uncertain type (BCUs). We aim at confirming the blazar nature of BCUs and test if new optical spectroscopic observations can reveal spectral features, allowing us to get a redshift estimate for known BL Lac objects. We also aim to search for and discover changing-look blazars (i.e., blazars that show a different classification at different epochs). We carry out an extensive search for optical spectra available in the Large Sky Area Multi-object Fibre Spectroscopic Telescope (LAMOST) Data Release 5 (DR5) archive. We select sources out of the 4FGL catalog, the list of targets from our follow-up spectroscopic campaign of unidentified or unassociated {gamma}-ray sources, and the multifrequency catalog of blazars: the Roma-BZCAT. We select a total of 392 spectra. We also compare some of the LAMOST spectra with those available in the literature. We classify 20 BCUs confirming their blazar-like nature. Then we obtain 15 new redshift estimates for known blazars. We discover 26 transitional (i.e., changing-look) blazars that changed their classification. Finally, we are able to confirm the blazar-like nature of six BL Lac candidates. All remaining sources analyzed agree with previous classifications. BL Lac objects are certainly the most elusive type of blazars in the {gamma}-ray extragalactic sky.
54. An Ultraviolet Atlas of Quasar and Blazar Spectra
ID:
ivo://CDS.VizieR/III/157
Title:
An Ultraviolet Atlas of Quasar and Blazar Spectra
Short Name:
III/157
Date:
21 Oct 2021
Publisher:
CDS
Description:
This atlas contains the ultraviolet spectra of 70 quasars, blazars, and Seyfert 1 galaxies that were produced by combining over 100 low resolution spectra from the International Ultraviolet Explorer (IUE) data archive. The spectra have been extracted with an optimal algorithm (see Kinney et al. 1991) and co-added to produce spectra with the best possible signal-to-noise ratio.
55. APM 08279+5255 CO(4-3) spectrum
ID:
ivo://CDS.VizieR/J/A+A/608/A30
Title:
APM 08279+5255 CO(4-3) spectrum
Short Name:
J/A+A/608/A30
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have performed a high sensitivity observation of the UFO/BAL quasar APM 08279+5255 at z=3.912 with NOEMA at 3.2mm, aimed at detecting fast moving molecular gas. We report the detection of blueshifted CO(4-3) with maximum velocity (v95%) of -1340km/s, with respect to the systemic peak emission, and a luminosity of L'=9.9x10^9^{mu}^-1^K.km/s/pc^2^, where {mu} is the lensing magnification factor. We discuss various scenarios for the nature of this emission and conclude that this is the first detection of fast molecular gas at redshift >3. We derived a mass flow rate of molecular gas in the range dM/dt=3-7.4x10^3^M_{sun}_/yr and momentum boost (dP_OF_/dt)/(dP_AGN_/dt)~2-6, which is therefore consistent with a momentum conserving flow. For the largest dP_OF_ the scaling is also consistent with an energy conserving flow with an efficiency of ~10-20%. The present data can hardly discriminate between the two expansion modes. The mass loading factor of the molecular outflow {eta}=(dM_OF_/dt)/SFR is >>1. We also detected a molecular emission line at a frequency of 94.83GHz corresponding to a rest-frame frequency of 465.8GHz; we tentatively identified this frequency with the cation molecule N_2_H^+^(5-4), which would be the first detection of this species at high redshift. We discuss the alternative possibility that this emission is due to a CO emission line from the, so far undetected, lens galaxy. Further observations of additional transitions of the same species with NOEMA can discriminate between the two scenarios.
56. APM 08279+5255 optical-to-UV spectrum
ID:
ivo://CDS.VizieR/J/A+A/617/A118
Title:
APM 08279+5255 optical-to-UV spectrum
Short Name:
J/A+A/617/A118
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the analysis of the rest-frame optical-to-UV spectrum of APM 08279+5255, a well-known lensed broad absorption line (BAL) quasar at z=3.911. The spectroscopic data are taken with the optical DOLoRes and near-IR NICS instruments at TNG, and include the previously unexplored range between CIII] {lambda}1910 and [OIII] {lambda}{lambda}4959,5007. We investigate the possible presence of multiple BALs by computing "balnicity" and absorption indexes (i.e. BI, BI_0_ and AI) for the transitions SiIV {lambda}1400, CIV {lambda}1549, AlIII {lambda}1860 and MgII {lambda}2800. No clear evidence for the presence of absorption features is found in addition to the already known, prominent BAL associated to C IV, which supports a high-ionization BAL classification for APM 08279+5255. We also study the properties of the [OIII], H{beta} and MgII emission lines. We find that [OIII] is intrinsically weak (F_[OIII]_/F_H{beta}_<~0.04), as it is typically found in luminous quasars with a strongly blueshifted CIV emission line (2500km/s for APM 08279+5255). We compute the single-epoch black hole mass based on MgII and H{beta} broad emission lines, finding M_BH_=(2/3)*10^10^{mu}^-1^M_{sun}_, with the magnification factor {mu} that can vary between 4 and 100 according to CO and rest-frame UV-to-mid-IR imaging respectively. Using a MgII equivalent width (EW)-to-Eddington ratio relation, the EW_MgII_~27{AA} measured for APM 08279+5255 translates into an Eddington ratio of ~0.4, which is more consistent with {mu}=4. This magnification factor also provides a value of M_BH_ that is consistent with recent reverberation-mapping measurements derived from CIV and SiIV.
57. Arp 102B spectral optical monitoring
ID:
ivo://CDS.VizieR/J/A+A/559/A10
Title:
Arp 102B spectral optical monitoring
Short Name:
J/A+A/559/A10
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results of long-term (1987-2010) optical spectral monitoring of the broad-line radio galaxy Arp 102B, a prototype of an active galactic nucleus with double-peaked broad emission lines that are commonly assumed to be emitted from an accretion disk. To explore the structure of the broad-line region (BLR), we analyze the light-curves of the broad H{alpha} and H{beta} lines and the continuum flux. We aim to estimate the dimensions of the broad-line emitting regions and the mass of the central black hole. We used the cross correlation function to find lags between the lines and continuum variations. We investigated the correlation between line and continuum fluxes in more detail, and explored periodical variations of the red-to-blue line flux ratio using Lomb-Scargle periodograms.
58. A search for faint blue stars.
ID:
ivo://CDS.VizieR/II/239
Title:
A search for faint blue stars.
Short Name:
II/239
Date:
21 Oct 2021
Publisher:
CDS
Description:
Continuing the survey for faint blue stars at high galactic latitudes of Haro and Luyten (1962, Cat. <III/74>, this search was made, following the Tonantzintla three image method, with the 48" Schmidt telescope of Mt. Palomar. In the first paper, a catalogue of 4431 stars and 84 compact objects found in nine PSS fields scattered around the NGP is presented, with the 1950 positions and the estimated magnitudes and colour classes. The catalogue contains also extensive identifications with previous surveys, including some known QSSs; 16 QSS candidates are proposed; spectra are available for most of the unknown stars brighter than 14mag. In the second paper, a catalogue of 2011 stars and compact objects is presented with the 1950 positions and the estimated magnitude and colour classes. Complementary to the catalogue of Haro and Luyten (1962BITon...3...37H) at declination +6{deg} and 0{deg} it contains also extensive identifications with previous surveys and known QSO's; candidate QSO's are indicated; spectra are available for some new blue stars. The third and last part of the survey of faint blue objects contains a catalogue of 2484 starlike or compact objects is presented with the 1950 positions, estimated magnitudes, color classes and extensive identifications with stars of previous surveys and known QSO's. The three parts were merged into a single file "catalog.dat".
59. Asiago Catalogue of QSOs
ID:
ivo://CDS.VizieR/VII/69
Title:
Asiago Catalogue of QSOs
Short Name:
VII/69
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Asiago Catalog of 2004 Quasi Stellar Objects (QSOs) is an updated version of that published by Barbieri, Capaccioli and Zambon in 1975 (1975MmSAI..46..461B). Most of the information of these objects are taken from the literature published before Dec. 31, 1981. Specifically, the catalog.dat file contains names, equatorial and galactic coordinates, photometry, redshifts, information on radio emission, variability, morphology, presence of absorption lines, for 2004 QSOs. The indexed references (in refs.dat) and further detailed information (in remarks.dat) concerning absorption spectra, X-ray properties, and cross-reference tables are also provided.
60. Asiago-ESO/RASS QSO survey. I.
ID:
ivo://CDS.VizieR/J/AJ/119/2540
Title:
Asiago-ESO/RASS QSO survey. I.
Short Name:
J/AJ/119/2540
Date:
21 Oct 2021
Publisher:
CDS
Description:
This paper presents the first results of a survey for bright quasars (V<14.5 and R<15.4) covering the northern hemisphere at Galactic latitudes |b|>30{deg}. The photometric database is derived from the Guide Star and USNO catalogs. Quasars are identified on the basis of their X-ray emission measured in the ROSAT All-Sky Survey. The surface density of quasars brighter than 15.5mag turns out to be (10+/-2)x10^-3^deg^-2^, about 3 times higher than that estimated by the Palomar-Green (PG) survey. The quasar optical luminosity function (LF) at 0.04<z<=0.3 is computed and shown to be consistent with a luminosity-dependent luminosity evolution of the type derived by La Franca & Cristiani (1997AJ....113.1517L) in the range 0.3<z<=2.2. The predictions of semianalytical models of hierarchical structure formation agree remarkably well with the present observations.