- ID:
- ivo://CDS.VizieR/J/MNRAS/383/581
- Title:
- Broad-line Balmer decrements in blue AGN
- Short Name:
- J/MNRAS/383/581
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have investigated the broad-line Balmer decrements (H{alpha/H{beta}) for a large, homogeneous sample of Seyfert 1 galaxies and quasi-stellar objects (QSOs) using spectroscopic data obtained in the Sloan Digital Sky Survey. The sample, drawn from the Fourth Data Release, comprises 446 low-redshift (z<=0.35) active galactic nuclei (AGN) that have blue optical continua as indicated by the spectral slopes in order to minimize the effect of dust extinction. We find that (i) the distribution of the intrinsic broad-line H{alpha}/H{beta} ratio can be well described by log-Gaussian, with a peak at H{alpha}/H{beta}=3.06 and a standard deviation of about 0.03dex only; (ii) the Balmer decrement does not correlate with AGN properties such as luminosity, accretion rate and continuum slope, etc.; (iii) on average, the Balmer decrements are found to be only slightly larger in radio-loud sources (3.37) and sources having double-peaked emission-line profiles (3.27) compared to the rest of the sample. We therefore suggest that the broad-line H{alpha}/H{beta} ratio can be used as a good indicator for dust extinction in the AGN broad-line region; this is especially true for radio-quiet AGN with regular emission-line profiles, which constitute the vast majority of the AGN population.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/764/5
- Title:
- BR photometry of 2012 precursor flare in OJ287
- Short Name:
- J/ApJ/764/5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have studied three most recent precursor flares in the light curve of the blazar OJ 287 while invoking the presence of a precessing binary black hole in the system to explain the nature of these flares. Precursor flare timings from the historical light curves are compared with theoretical predictions from our model that incorporate effects of an accretion disk and post-Newtonian description for the binary black hole orbit. We find that the precursor flares coincide with the secondary black hole descending toward the accretion disk of the primary black hole from the observed side, with a mean z-component of approximately z_c_=4000AU. We use this model of precursor flares to predict that precursor flare of similar nature should happen around 2020.96 before the next major outburst in 2022.
- ID:
- ivo://CDS.VizieR/J/A+A/559/A29
- Title:
- BR 1202-0725 system in [CII] line
- Short Name:
- J/A+A/559/A29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We performed a kinematical analysis of the [CII] line emission of the BR 1202-0725 system at z~4.7 using ALMA science verification observations. The most prominent sources of this system are a quasar (QSO) and a submillimeter galaxy (SMG), separated by a projected distance of about ~24kpc and characterized by very high star formation rates, higher than 1000M_{sun}_/yr. However, the ALMA observations reveal that these galaxies apparently have undisturbed rotating disks, which is at variance with the commonly accepted scenario in which strong star formation activity is induced by a major merger.We also detected faint components which, after spectral deblending, were spatially resolved from the main QSO and SMG emissions. The relative velocities and positions of these components are compatible with orbital motions within the gravitational potentials generated by the QSO host galaxy and the SMG, suggesting that they are smaller galaxies in interaction or gas clouds in accretion flows of tidal streams. Moreover, we did not find any clear spectral evidence for outflows caused by active galactic nuclei or stellar feedback. This suggests that the high star formation rates might be induced by interactions or minor mergers with these companions, which do not affect the large-scale kinematics of the disks, however. Alternatively, the strong star formation may be fueled by the accretion of pristine gas from the host halo. Our kinematical analysis also indicates that the QSO and the SMG have similar dynamical masses, mostly in the form of molecular gas, and that the QSO host galaxy and the SMG are seen close to face-on with slightly different disk inclinations: the QSO host galaxy is seen almost face-on (i~15{deg}), while the SMG is seen at higher inclinations (i~25{deg}). Finally, the ratio between the black hole mass of the QSO, obtained from new X-shooter spectroscopy, and the dynamical mass of the host galaxy is similar to value found in very massive local galaxies, suggesting that the evolution of black hole galaxy relations is probably better studied with dynamical than with stellar host galaxy masses.
114. B3-VLA CSS sample
- ID:
- ivo://CDS.VizieR/J/A+A/426/463
- Title:
- B3-VLA CSS sample
- Short Name:
- J/A+A/426/463
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of VLBA observations at 6 and 3.6cm for eighteen Compact Steep Spectrum radio sources (CSS) from the B3-VLA CSS sample. In most cases these VLBA images display a "Double/Triple" morphology, and the core is unambiguously detected in seven sources. Multifrequency images allow us to study the spectral properties of the individual source components and to constrain the spectral age. In lobe-dominated sources the radiative ages deduced from the synchrotron theory are in the range of up 5x10^3^ years, if equipartition magnetic field is assumed. Polarized emission is detected at a few percent level for two sources only. They were the only two sources displaying polarized emission in VLA A configuration data, and this implies that beam depolarization is not effective in reducing the integrated fractional polarization for these sources.
- ID:
- ivo://CDS.VizieR/J/AJ/138/845
- Title:
- BVRI observations of 235 bright quasars
- Short Name:
- J/AJ/138/845
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometric observations of 235 extragalactic objects that are potential targets for the Space Interferometry Mission (SIM) are presented. Mean B, V, R, I magnitudes at the 5% level are obtained at 1-4 epochs between 2005 and 2007 using the 1m telescopes at Cerro Tololo Inter-American Observatory and the Naval Observatory Flagstaff Station. Of the 134 sources that have V magnitudes in the Veron & Veron-Cetty catalog (Cat. VII/248), a difference of over 1.0mag is found for the observed-catalog magnitudes for about 36% of the common sources, and 10 sources show over 3mag difference. Our first set of observations presented here form the basis of a long-term photometric variability study of the selected reference frame sources to assist in mission target selection and to support QSO multicolor photometric variability studies in general.
- ID:
- ivo://CDS.VizieR/J/A+AS/128/315
- Title:
- BVRI photometry of blazars
- Short Name:
- J/A+AS/128/315
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of both BVRI CCD photometric monitoring and fast photometry for 8 blazars and variable quasars are presented. There is intraday variability for 6 blazars and very short timescales (minutes to two hours) variability for 5 objects. Implications for relativistic beaming are briefly discussed.
- ID:
- ivo://CDS.VizieR/J/A+A/450/39
- Title:
- BVRI photometry of 8 red blazars
- Short Name:
- J/A+A/450/39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 2482 BVRI photometric data on eight red blazars taken from 3 Observatories in the period 2003 September - 2004 February are presented. A table is given, containing the source name, the observation time, the source magnitude, the error on the source magnitude, the photometric band, and a label indicating the Observatory where the observation was done.
- ID:
- ivo://CDS.VizieR/J/MNRAS/444/1747
- Title:
- CaII absorbers in SDSS QSOs
- Short Name:
- J/MNRAS/444/1747
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a survey for CaII {lambda}{lambda}3934,3969 absorption-line systems culled from ~95000 Sloan Digital Sky Survey (SDSS) Data Release 7 and Data Release 9 quasar spectra. With 435 doublets identified in the catalogue, this list is the largest CaII catalogue compiled to date, spanning redshifts z<1.34, which corresponds to the most recent ~8.9Gyr of the history of the Universe. We derive statistics on the Caii rest equivalent width distribution and incidence. We find that the {lambda}3934 rest equivalent width (W_0_^{lambda}3934^) distribution cannot be described by a single exponential function. A double exponential function is required to produce a satisfactory description.
- ID:
- ivo://CDS.VizieR/J/AJ/153/157
- Title:
- Candidate ICRF flat-spectrum radio sources. III.
- Short Name:
- J/AJ/153/157
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In extending our spectroscopic program, which targets sources drawn from the International Celestial Reference Frame (ICRF) Catalog, we have obtained spectra for ~160 compact, flat-spectrum radio sources and determined redshifts for 112 quasars and radio galaxies. A further 14 sources with featureless spectra have been classified as BL Lac objects. Spectra were obtained at three telescopes: the 3.58m European Southern Observatory New Technology Telescope, and the two 8.2m Gemini telescopes in Hawaii and Chile. While most of the sources are powerful quasars, a significant fraction of radio galaxies is also included from the list of non-defining ICRF radio sources.
- ID:
- ivo://CDS.VizieR/J/MNRAS/435/3306
- Title:
- Candidate type II QSOs in SDSS III
- Short Name:
- J/MNRAS/435/3306
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- At low redshifts, dust-obscured quasars often have strong yet narrow permitted lines in the rest-frame optical and ultraviolet, excited by the central active nucleus, earning the designation type II quasars. We present a sample of 145 candidate type II quasars at redshifts between 2 and 4.3, encompassing the epoch at which quasar activity peaked in the universe. These objects, selected from the quasar sample of the Baryon Oscillation Spectroscopic Survey of the Sloan Digital Sky Survey III, are characterized by weak continuum in the rest-frame ultraviolet (typical continuum magnitude of i~22) and strong lines of CIV and Ly{alpha}, with full width at half-maximum less than 2000km/s. The continuum magnitudes correspond to an absolute magnitude of -23 or brighter at redshift 3, too bright to be due exclusively to the host galaxies of these objects. Roughly one third of the objects are detected in the shorter wavelength bands of the Wide-Field Infrared Survey Explorer survey; the spectral energy distributions of these objects appear to be intermediate between classic type I and type II quasars seen at lower redshift. Five objects are detected at rest frame 6{mu}m by Spitzer, implying bolometric luminosities of several times 10^46^erg/s. We have obtained polarization measurements for two objects; they are roughly 3 percent polarized. We suggest that these objects are luminous quasars, with modest dust extinction (A_V_~0.5mag), whose ultraviolet continuum also includes a substantial scattering contribution. Alternatively, the line of sight to the central engines of these objects may be obscured by optically thick material whose covering fraction is less than unity.
