- ID:
- ivo://CDS.VizieR/J/MNRAS/450/3568
- Title:
- Non-Fermi blazar sample
- Short Name:
- J/MNRAS/450/3568
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- By statistically analysing a large sample that includes Fermi-detected blazars (FBs) and non-Fermi-detected blazars (NFBs), we find that there are significant differences between FBs and NFBs in redshift, black hole mass, jet kinetic power from cavity power, broad-line luminosity and the ratio of core luminosity to absolute V-band magnitude (Rv), but not in the ratio of the radio core to extended flux (Rc) and the Eddington ratio. Compared with NFBs, FBs have larger mean jet power, Rc and Rv, while having smaller mean redshift, black hole mass and broad-line luminosity. These results support the fact that the beaming effect is the main reason for differences between FBs and NFBs, and that FBs are likely to have a more powerful jet. For both FBs and NFBs, there are significant correlations between the jet power and the accretion rate (traced by the broad-emission line luminosity), and between the jet power and the black hole mass. For FBs, the black hole mass does not have a significant influence on jet power, while for NFBs, both the accretion rate and black hole mass contribute to the jet power. Our results support the 'blazar sequence' and show that the synchrotron peak frequency ({nu}peak) is associated with the accretion rate but not with the black hole mass.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/300/323
- Title:
- NOT GL survey of multiply imaged quasars
- Short Name:
- J/A+A/300/323
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A gravitational lens (GL)-search program, initiated in 1990 at the Nordic Optcal Telescope (NOT), has revealed several possible GL-candidates among a sample of 168 quasars (QSOs), chosen from three lists compiled by C. Hazard, D. Reimers and J. Surdej, respectively. Some of these candidates, selected for having close companions (within 5 arcseconds), were imaged in several filters and their colours compared. Low dispersion spectra of the most promising candidates were also obtained at the NOT and ESO New Technology Telescope (NTT). None of these has proved to be strong candidates of gravitational lensing effects. We present this new sample of QSOs and combine it with previously published optical QSO samples in a statistical analysis to yield constraints on flat cosmologies and galaxy velocity dispersions.
533. NVSS radio quasars
- ID:
- ivo://CDS.VizieR/J/other/AcApS/20.366
- Title:
- NVSS radio quasars
- Short Name:
- J/other/AcApS/20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have searched 11304 quasars from the NVSS catalog for radio emission and obtained 2626 positive detections, of which 301 are new radio detections. We made statistical studies of the radio spectral index, radio luminosity and the fraction of radio-loud quasars versus absolute B magnitude and redshift. We found that the fraction rises between M_B_=-22 and -30 and that it increases at z=0.0 until z=0.8, then goes down at z=1.5. The degree of polarization shows no dependence on redshift.
- ID:
- ivo://CDS.VizieR/J/A+A/626/A9
- Title:
- Obscured AGN at 1.5<z<3.0
- Short Name:
- J/A+A/626/A9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We select a sample of 90 obscured (type 2) AGN with 1.45<z<3.05 from the zCOSMOS-deep galaxy sample by 5 sigma-detection of the high-ionization CIV {lambda}1549 narrow emission line. The presence of this feature in a galaxy spectrum is often associated with nuclear activity, and the selection effectiveness has been also confirmed by ultraviolet (UV) emission line ratio diagnostic diagrams. Applying the same selection technique, a sample of 102 unobscured (type 1) AGN was collected. Taking advantage of the large amount of multi-band data available in the COSMOS field, we investigate the properties of the CIV-selected type 2 AGN, focusing on their host galaxies, X-ray emission and UV emission lines. Finally, we investigate the physical properties of the ionized gas in the Narrow Line Region (NLR) of this type 2 AGN sample, combining the analysis of strong UV emission lines with predictions from photo-ionization models. We find that, in order to successfully reproduce the relative intensity of UV emission lines of the selected high-z type 2 AGN, two new ingredients in the photo-ionization models are fundamental,i.e. small inner radii of the NLR (~90pc for LAGN=10^45^erg/s) and the internal dissipative micro-turbulence of the gas emitting clouds (with v_micr_~100km/s). With these modified models, we compute the gas-phase metallicity of the NLR, and our measurements indicate a statistically significant evolution of the metal content with redshift. Finally, we do not observe, in our CIV-selected type 2 AGN sample, a strong relationship between the NLR gas metallicity and the stellar mass of the host galaxy.
- ID:
- ivo://CDS.VizieR/J/ApJ/883/163
- Title:
- OI abs. search in Keck and VLT spectra of 199 QSOs
- Short Name:
- J/ApJ/883/163
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a survey for metal absorption systems traced by neutral oxygen over 3.2<z<6.5. Our survey uses Keck/ESI and VLT/X-Shooter spectra of 199 QSOs with redshifts up to 6.6. In total, we detect 74 OI absorbers, of which 57 are separated from the background QSO by more than 5000km/s. We use a maximum likelihood approach to fit the distribution of OI{lambda}1302 equivalent widths in bins of redshift and from this determine the evolution in number density of absorbers with W_1302_>0.05{AA}, of which there are 49 nonproximate systems in our sample. We find that the number density does not monotonically increase with decreasing redshift, as would naively be expected from the buildup of metal-enriched circumgalactic gas with time. The number density over 4.9<z<5.7 is a factor of 1.7-4.1 lower (68% confidence) than that over 5.7<z<6.5, with a lower value at z<5.7 favored with 99% confidence. This decrease suggests that the fraction of metals in a low-ionization phase is larger at z~6 than at lower redshifts. Absorption from highly ionized metals traced by CIV is also weaker in higher-redshift OI systems, supporting this picture. The evolution of OI absorbers implies that metal-enriched circumgalactic gas at z~6 is undergoing an ionization transition driven by a strengthening ultraviolet background. This in turn suggests that the reionization of the diffuse intergalactic medium may still be ongoing at or only recently ended by this epoch.
- ID:
- ivo://CDS.VizieR/J/ApJ/549/155
- Title:
- [OIII] emission in a sample of AGNs
- Short Name:
- J/ApJ/549/155
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The emission-line flux ratio of [OIII]4363/[OIII]5007 (R_OIII_) is a useful diagnostic for the ionization mechanism and physical properties of emission-line regions in active galactic nuclei (AGNs). However, it is known that simple photoionization models underpredict the [OIII]4363 intensity, being inconsistent with observations. In this paper we report on several pieces of evidence that a large fraction of the [OIII]4363 emission arises from the dense gas obscured by putative tori: (1) the visibility of high-R_OIII_ regions is correlated to that of broad-line regions, (2) higher R_OIII_ objects show hotter mid-infrared colors, (3) higher R_OIII_ objects show stronger highly ionized emission lines such as [FeVII] 6087 and [FeX]6374, and (4) higher R_OIII_ objects have broader line width of [OIII]4363 normalized by that of [OIII]5007.
- ID:
- ivo://CDS.VizieR/J/A+A/591/A88
- Title:
- [OIII] of radio-emitting narrow-line Seyfert 1
- Short Name:
- J/A+A/591/A88
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The [OIII] {lambda}{lambda} 4959, 5007 lines are a useful proxy to test the kinematic of the narrow-line region (NLR) in active galactic nuclei (AGN). In AGN, and particularly in narrow-line Seyfert 1 galaxies (NLS1s) these lines often show few peculiar features, such as blue wings, often interpreted as outflowing component, and a shift - typically toward lower wavelengths - of the whole spectroscopic feature in some exceptional sources, the so-called blue outliers, which are often associated to strong winds. We investigated the incidence of these peculiarities in two samples of radio-emitting NLS1s, one radio-loud and one radio-quiet. We also studied a few correlations between the observational properties of the [OIII] lines and those of the AGN. Our aim was to understand the difference between radio-quiet and radio-loud NLS1s, which may in turn provide useful information on the jet formation mechanism. We find that the NLR gas is much more perturbed in radio-loud than in radio-quiet NLS1s. In particular the NLR dynamics in {gamma}-ray emitting NLS1s appears to be highly disturbed, and this might be a consequence of interaction with the relativistic jet. The less frequently perturbed NLR in radio-quiet NLS1s suggests instead that these sources likely do not harbor a fully developed relativistic jet. Nonetheless blue-outliers in radio-quiet NLS1s are observed, and we interpret them as a product of strong winds.
- ID:
- ivo://CDS.VizieR/J/A+AS/115/75
- Title:
- Optical astrometry of Benchmark radio sources. III
- Short Name:
- J/A+AS/115/75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Optical positions, relative to the International Reference Stars catalogue (IRS), and therefore in the system of the FK5, have been obtained for the optical counterparts of 35 extragalactic radio sources south of {delta}~+3deg. Many of these sources are being considered as possible Benchmark objects for the establishment of a quasi-inertial unified radio/optical reference frame. Precision levels better than 0.2" in both coordinates were achieved. A comparison with VLBI radio positions available for these sources is presented. We give evidence for a possible offset in RA between the radio and optical reference frames.
- ID:
- ivo://CDS.VizieR/J/ApJ/596/768
- Title:
- Optical depths in 19 QSOs
- Short Name:
- J/ApJ/596/768
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We measure the distribution of carbon in the intergalactic medium as a function of redshift z and overdensity {delta}. Using a hydrodynamical simulation to link the H I absorption to the density and temperature of the absorbing gas, and a model for the UV background radiation, we convert ratios of C IV to H I pixel optical depths into carbon abundances. For the median metallicity this technique was described and tested in Paper I (Aguirre et al., 2002ApJ...576....1A) of this series. Here we generalize it to reconstruct the full probability distribution of the carbon abundance and apply it to 19 high-quality quasar absorption spectra.
- ID:
- ivo://CDS.VizieR/J/A+A/540/A132
- Title:
- Optical follow-up of Q0957+561 in 2005-2010
- Short Name:
- J/A+A/540/A132
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The optical variability database of the two images (A and B) of the gravitationally lensed quasar Q0957+561 is based on frames taken with the Liverpool Robotic Telescope in the 2005-2010 period, as part of the Liverpool Quasar Lens Monitoring (LQLM) project (Goicoechea et al. 2010AdAst2010E..29G). A crowded-field photometry pipeline produced instrumental fluxes of both quasar images, and only frames with signal-to-noise ratio above 80 over Q0957+561A were passed through a transformation pipeline. This pipeline transformed instrumental magnitudes into SDSS magnitudes (the calibration-correction scheme is described in Appendix A of Shalyapin et al. (2008A&A...492..401S) and the main text of the paper). We also turned SDSS magnitudes into physical fluxes using suitable conversion equations (SDSS Photometric Flux Calibration 2007, http://www.sdss.org/dr7/algorithms/fluxcal.html). Table 1 contains g-band fluxes for 357 different nights, while Table 2 includes r-band fluxes for 371 observation nights.
