- ID:
- ivo://CDS.VizieR/J/ApJS/189/1
- Title:
- A 3.5mm polarimetric survey of radio-loud AGNs
- Short Name:
- J/ApJS/189/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results from the first large (>100 sources) 3.5mm polarimetric survey of radio-loud active galactic nuclei (AGNs). This wavelength is favorable within the radio-millimeter range for measuring the intrinsic linearly polarized emission from AGNs, since in general it is only marginally affected by Faraday rotation of the electric vector position angle and depolarization. The I, Q, U, and V Stokes parameter observations were performed with the XPOL polarimeter at the IRAM 30m Telescope on different observing epochs from 2005 July (when most of the measurements were made) to 2009 October. Our sample consists of 145 flat-radio-spectrum AGNs with declination >-30{deg} (J2000.0) and flux density >~1Jy at ~86GHz, as measured at the IRAM 30m Telescope from 1978 to 1994. This constraint on the radio spectrum causes our sample to be dominated by blazars, which allows us to conduct new statistical studies on this class of high-luminosity, relativistically beamed emitters. Over our entire source sample, the luminosity of the jets is anticorrelated with the degree of linear polarization. Consistent with previous findings claiming larger Doppler factors for brighter {gamma}-ray blazars, quasars listed in our sample, and in the Fermi Large Area Telescope Bright Source Catalog (LBAS, Abdo et al., 2009ApJ...700..597A), show larger luminosities than non-LBAS ones, but our data do not allow us to confirm the same for BL Lac objects. Our new data can be used to estimate the 3.5mm AGN contribution to measurements of the linear polarization of the cosmic microwave background, such as those performed by the Planck satellite.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/571/665
- Title:
- Analysis of the Ly{alpha} forest at z=0-5. V.
- Short Name:
- J/ApJ/571/665
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In Paper III (Bechtlod et al., 2002, Cat. <J/ApJS/140/143>) of our series, "A Uniform Analysis of the Ly{alpha} Forest at z=0-5", we presented a set of 270 quasar spectra from the archives of the Faint Object Spectrograph (FOS) on the Hubble Space Telescope (HST). A total of 151 of these spectra, yielding 906 lines, are suitable for using the proximity effect signature to measure J({nu}_0_), the mean intensity of the hydrogen-ionizing background radiation field, at low redshift.
- 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.
- 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.
- 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.
- 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.
- 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".
- 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.
- 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.
- ID:
- ivo://CDS.VizieR/J/AJ/124/2955
- Title:
- Asiago-ESO/RASS QSO survey. II.
- Short Name:
- J/AJ/124/2955
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the second paper of a series describing the Asiago-ESO/RASS QSO survey, a project aimed at the construction of an all-sky, statistically well defined sample of very bright QSOs (BJ<=15). Such a survey is required to remove the present uncertainties about the properties of the local QSO population and constitutes an homogeneous database for detailed evolutionary studies of active galactic nuclei (AGNs). We present here the complete southern sample, which comprises 243 bright (12.60<=BJ<=15.13) QSO candidates at high galactic latitudes (|b_gal_|>=30{deg}). The area covered by the survey is 5660deg^2^. Spectroscopy for the 137 still unidentified objects has been obtained. The total number of AGNs turns out to be 11163 of which are new identifications. The properties of the selection are discussed. The completeness and the success rate for this survey at the final stage are 63% and 46%, respectively.
