- ID:
- ivo://CDS.VizieR/J/A+A/564/A117
- Title:
- Binary quasars from LQAC-2
- Short Name:
- J/A+A/564/A117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Thanks to huge surveys, such as the Sloan Digital Sky Survey (SDSS), the last decade has shown a dramatic increase in the number of known quasars. In the second release of the general compiled catalogue Large Quasar Astrometric Catalogue (LQAC), 187504 objects are recorded. From this catalogue, we carry out statistical studies dealing with several topics: the astrometric accuracy of the quasars, their spatial location, the distribution of the distance to the closest neighbour, the identification of binary quasars, the completness of catalogues at a given magnitude and the estimation of the number of quasars expected to be detected by the astrometric space mission Gaia. We analyse the astrometric improvements brought by the LQAC-2 in terms of equatorial coordinates off-sets. We plot the bi-dimensional spatial distribution of the LQAC-2 quasars according to their equatorial, galactic, and ecliptic coordinates, thus exploring the anisotropy of the distribution. We compare the observed distribution of closest neighbours with the theoretical values based on a Poisson distribution. Moreover, we perform a comparison between two catalogues, the SDSS and the 2dF inside a huge common field. By extrapolating to the whole sky we deduce the number of quasars that will be detected by Gaia.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/131/1
- Title:
- Binary quasars in the SDSS
- Short Name:
- J/AJ/131/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of 221 new quasar pairs with proper transverse separations R_prop_<1h^1^Mpc over the redshift range 0.5<z<3.0, discovered from an extensive follow-up campaign to find companions around the Sloan Digital Sky Survey (Cat. <VII/243>) and 2dF QSO Redshift Survey (Cat. <VII/241>) quasars. This sample includes 26 new binary quasars with separations R_prop_<50h^-1^kpc ({thetas}<10"), more than doubling the number of such systems known. We define a statistical sample of binaries selected with homogeneous criteria and compute its selection function, taking into account sources of incompleteness. The first measurement of the quasar correlation function on scales 10h^-1^kpc<R_prop_<400h^-1^kpc is presented.
- ID:
- ivo://CDS.VizieR/J/MNRAS/357/1267
- Title:
- b_j_ur photometry and redshifts of QSOs
- Short Name:
- J/MNRAS/357/1267
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The quasar sample selected by cross-correlating the Faint Images of the Radio Sky at Twenty cm (FIRST, <VIII/71>) survey and the 2-degree Field Quasar Redshift Survey (2QZ, <VII/223>) allows us to explore, for the first time, the faint end of the radio and optical luminosity functions up to z=~2.2. We find indications (~3{sigma}) of a negative evolution for these faint sources at z>~1.8, both in radio and optical bands. This corresponds to a decrement in the space density of faint quasars of approximately a factor 2 at z=2.2 and confirms the presence of a differential evolution for the population of radio-active quasars. The faint end of both luminosity functions flattens and the comparison with the (optical) number density of the whole quasar population supports a dependence of the fraction of radio-detected quasars on the optical luminosity. A progressive decrease in the fraction of quasars in the whole radio source population can be consistently accounted for within the receding torus scenario. The population of low-luminosity quasars, which the FIRST-2dF detects, appears to depart from the classical scheme for radio-loud quasars.
- ID:
- ivo://CDS.VizieR/J/ApJ/614/91
- Title:
- Black hole mass and accretion rate of AGNs
- Short Name:
- J/ApJ/614/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using an empirical relation between the broad-line region size and optical continuum luminosity, we estimated the black hole mass and accretion rate for 135 active galactic nuclei (AGNs) with double-peaked broad emission lines in two samples, one from the Sloan Digital Sky Survey (SDSS, Cat. <J/AJ/126/2579>) and the other from a survey of radio-loud broad emission line AGNs (Eracleous & Halpern, 2003, Cat. <J/ApJ/599/886>).
- ID:
- ivo://CDS.VizieR/J/MNRAS/478/4068
- Title:
- BLAGNs and NLS1s characteristics.
- Short Name:
- J/MNRAS/478/4068
- Date:
- 10 Dec 2021 00:54:07
- Publisher:
- CDS
- Description:
- investigated narrow-line Seyfert 1 galaxies (NLS1s) at optical, mid-infrared (MIR), and X-ray wavelengths, comparing them to the broad-line active galactic nuclei (BLAGNs). We found that black hole mass, coronal line luminosities, X-ray hardness ratio and X-ray, and optical and MIR luminosities are higher for the BLAGNs than for NLS1s, while policyclic aromatic hydrocarbon (PAH) contribution and the accretion rates are higher for NLS1s. Furthermore, we found some trends among spectral parameters that NLS1s have and BLAGNs do not have. The evolution of FWHM(H{beta}) with the luminosities of MIR and coronal lines, continuum luminosities, PAH contribution, H{beta} broad line luminosity, FWHM[OIII], and EW(H{beta}NLR) are important trends found for NLS1s. That may contribute to the insight that NLS1s are developing AGNs, growing their black holes, while their luminosities and FWHM(H{beta}) consequently grow, and that BLAGNs are mature, larger objects of slower and/or different evolution. Black hole mass is related to PAH contribution only for NLS1s, which may suggest that PAHs are more efficiently destroyed in NLS1s.
- ID:
- ivo://CDS.VizieR/J/ApJ/867/131
- Title:
- Blazar candidates behind the Magellanic Clouds
- Short Name:
- J/ApJ/867/131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the identification of blazar candidates behind the Magellanic Clouds. The objects were selected from the Magellanic Quasars Survey (MQS), which targeted the entire Large Magellanic Cloud (LMC) and 70% of the Small Magellanic Cloud (SMC). Among the 758 MQS quasars and 898 of the unidentified (featureless spectra) objects, we identified a sample of 44 blazar candidates, including 27 flat-spectrum radio quasars and 17 BL Lacertae objects, respectively. All the blazar candidates from our sample were identified with respect to their radio, optical, and midinfrared properties. The newly selected blazar candidates possess the long-term, multicolor photometric data from the Optical Gravitational Lensing Experiment, multicolor midinfrared observations, and archival radio data for one frequency at least. In addition, for nine of them, the radio polarization data are available. With such data, these objects can be used to study the physics behind the blazar variability detected in the optical and midinfrared bands, as a tool to investigate magnetic field geometry of the LMC and SMC, and as an exemplary sample of point-like sources most likely detectable in the {gamma}-ray range with the newly emerging Cherenkov Telescope Array.
- ID:
- ivo://CDS.VizieR/J/A+A/556/A71
- Title:
- Blazar 0836+710 long-term multiwavelength studies
- Short Name:
- J/A+A/556/A71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The observation of gamma-ray flares from blazar 0836+710 in 2011, following a period of quiescence, offered an opportunity to study correlated activity at different wavelengths for a high-redshift (z=2.218) active galactic nucleus. Optical and radio monitoring, plus Fermi-LAT gamma-ray monitoring provided 2008-2012 coverage, while Swift offered auxiliary optical, ultraviolet, and X-ray information. Other contemporaneous observations were used to construct a broad-band spectral energy distribution.
- ID:
- ivo://CDS.VizieR/J/PASJ/55/947
- Title:
- Blazars and Seyfert galaxies accretion rates
- Short Name:
- J/PASJ/55/947
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Accretion rates and their correlation with cosmological redshifts for a sample of blazars and Seyfert galaxies are presented. The sample includes 77 blazars (28 FSRQs, 26 LBLs, and 23 HBLs) and 60 Seyfert galaxies, of which the extended spectral energy distribution information and redshifts are available. Within the framework of accreting black holes, the accretion rates for these sources were estimated based on their bolometric luminosities.
89. Blazar sequence
- ID:
- ivo://CDS.VizieR/J/MNRAS/451/2750
- Title:
- Blazar sequence
- Short Name:
- J/MNRAS/451/2750
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on a large Fermi blazar sample, the blazar sequence (synchrotron peak frequency {nu}_peak_ versus synchrotron peak luminosity L_peak_) is revisited. It is found that there is significant anticorrelation between {nu}_peak_ and L_peak_ for blazars. However, after Doppler correction the anticorrelation disappears. The jet cavity power (P_jet_) is estimated from the extended radio luminosity so that it is free of beaming effects. We find that there are significant anticorrelations between P_jet_ and the beam-corrected {nu}_peak_' for both blazars and radio galaxies, which supports the blazar sequence and the unification of blazars and radio galaxies (an alternative relationship is the correlation between jet power and {gamma}-ray photon index).
- ID:
- ivo://CDS.VizieR/J/MNRAS/351/83
- Title:
- Blazars equivalent widths and radio luminosity
- Short Name:
- J/MNRAS/351/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Blazars are currently separated into BL Lacertae objects (BL Lacs) and flat spectrum radio quasars based on the strength of their emission lines. This is performed rather arbitrarily by defining a diagonal line in the Ca H&K break value-equivalent width plane, following Marcha et al. (1996MNRAS.281..425M). We readdress this problem and put the classification scheme for blazars on firm physical grounds. We study ~100 blazars and radio galaxies from the Deep X-ray Radio Blazar Survey (DXRBS, Cat. <J/AJ/115/1253> and <J/MNRAS/323/757>) and 2-Jy radio survey and find a significant bimodality for the narrow emission line [OIII]{lambda}5007. This suggests the presence of two physically distinct classes of radio-loud active galactic nuclei (AGN). We show that all radio-loud AGN, blazars and radio galaxies, can be effectively separated into weak- and strong-lined sources using the [OIII]{lambda}5007-[OII]{lambda}3727 equivalent width plane. This plane allows one to disentangle orientation effects from intrinsic variations in radio-loud AGN. Based on DXRBS, the strongly beamed sources of the new class of weak-lined radio-loud AGN are made up of BL Lacs at the ~75 per cent level, whereas those of the strong-lined radio-loud AGN include mostly (~97 per cent) quasars.