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Start Over Subject active galactic nuclei
631. Planck + X/{gamma} observations of blazars
ID:
ivo://CDS.VizieR/J/A+A/541/A160
Title:
Planck + X/{gamma} observations of blazars
Short Name:
J/A+A/541/A160
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present simultaneous Planck, Swift, Fermi, and ground-based data for 105 blazars belonging to three samples with flux limits in the soft X-ray, hard X-ray, and {gamma}-ray bands, with additional 5GHz flux-density limits to ensure a good probability of a Planck detection. We compare our results to those of a companion paper presenting simultaneous Planck and multi-frequency observations of 104 radio-loud northern active galactic nuclei selected at radio frequencies. While we confirm several previous results, our unique data set allows us to demonstrate that the selection method strongly influences the results, producing biases that cannot be ignored.
632. POGS-II ExGal catalog
ID:
ivo://CDS.VizieR/J/other/PASA/37.29
Title:
POGS-II ExGal catalog
Short Name:
J/other/PASA/37.
Date:
21 Oct 2021
Publisher:
CDS
Description:
The low-frequency linearly polarised radio source population is largely unexplored. However, a renaissance in low-frequency polarimetry has been enabled by pathfinder and precursor instruments for the Square Kilometre Array. In this second paper from the POlarised GaLactic and Extragalactic All-Sky MWA Survey-the POlarised GLEAM Survey, or POGS-we present the results from our all-sky MWA Phase I Faraday Rotation Measure survey. Our survey covers nearly the entire Southern sky in the Declination range -82{deg} to +30{deg} at a resolution between around three and seven arcminutes (depending on Declination) using data in the frequency range 169-231MHz. We have performed two targeted searches: the first covering 25489 square degrees of sky, searching for extragalactic polarised sources; the second covering the entire sky South of Declination +30{deg}, searching for known pulsars. We detect a total of 517 sources with 200MHz linearly polarised flux densities between 9.9mJy and 1.7Jy, of which 33 are known radio pulsars. All sources in our catalogues have Faraday rotation measures in the range -328.07rad/m^2^ to +279.62rad/m^2^. The Faraday rotation measures are broadly consistent with results from higher-frequency surveys, but with typically more than an order of magnitude improvement in the precision, highlighting the power of low-frequency polarisation surveys to accurately study Galactic and extragalactic magnetic fields. We discuss the properties of our extragalactic and known-pulsar source population, how the sky distribution relates to Galactic features, and identify a handful of new pulsar candidates among our nominally extragalactic source population.
633. Polar dust obscuration in broad-line AGN
ID:
ivo://CDS.VizieR/J/A+A/654/A93
Title:
Polar dust obscuration in broad-line AGN
Short Name:
J/A+A/654/A93
Date:
22 Feb 2022
Publisher:
CDS
Description:
We study a sample of 1275 broad-line AGN in the XMM-XXL field, with optical to infrared photometric data. These AGN are seen along their polar direction and we expect a maximal impact of dust located around the poles when it is present. We use X-CIGALE, which introduces a dust component to account for obscuration along the polar directions, modeled as a foreground screen, and an extinction curve that is chosen as it steepens significantly at short wavelengths or is much grayer. By comparing the results of different fits, we are able to define subsamples of sources with positive statistical evidence in favor of or against polar obscuration (if present) and described using the gray or steep extinction curve. We find a similar fraction of sources with positive evidence for and against polar dust. Applying statistical corrections, we estimate that half of our sample could contain polar dust and among them, 60% exhibit a steep extinction curve and 40% a flat extinction curve; although these latter percentages are found to depend on the adopted extinction curves. The obscuration in the V-band is not found to correlate with the X-ray column density, while A_V_/N_H_ ratios span a large range of values and higher dust temperatures are found with the flat, rather than with the steep extinction curve. Ignoring this polar dust component in the fit of the spectral energy distribution of these composite systems leads to an overestimation of the stellar contribution. A single fit with a polar dust component described with an SMC extinction curve efficiently overcomes this issue but it fails at identifying all the AGN with polar dust obscuration.
634. Positions of 790 AGNs
ID:
ivo://CDS.VizieR/J/A+AS/115/97
Title:
Positions of 790 AGNs
Short Name:
J/A+AS/115/97
Date:
21 Oct 2021
Publisher:
CDS
Description:
From the measurement on the Digitized Sky Survey of the optical position of 153 QSOs with an accurate VLBI position, we have determined that the r.m.s. uncertainties of these measurements is about 0.6 arcsec in both coordinates over the whole sky, except for objects located near the edge of the plates. We have measured the optical position of 790 AGNs (or AGNs candidates). For many of these objects, the accuracy of the published optical position was one arcminute or worst.
635. Profile variability in lines of NGC 5548
ID:
ivo://CDS.VizieR/J/A+A/422/925
Title:
Profile variability in lines of NGC 5548
Short Name:
J/A+A/422/925
Date:
21 Oct 2021
Publisher:
CDS
Description:
Between 1996 and 2002, we have carried out a spectral monitoring program for the Seyfert galaxy NGC 5548 with the 6m and 1m telescopes of SAO (Russia) and with the 2.1m telescope of Guillermo Haro Observatory (GHO) at Cananea, Mexico. High quality spectra with S/N>50 in the continuum near H{alpha} and H{beta} were obtained, covering the spectral range ~(4000-7500){AA} with a (4.5 to 15){AA}-resolution. We found that both the flux in the lines and the continuum gradually decreased, reaching minimum values during May-June 2002. In the minimum state, the wings of H{beta} and H{alpha} became extremely weak, corresponding to a Sy1.8 type, not to a Sy1, as observed previously when the nucleus was brighter. The line profiles were decomposed into variable and constant components. The variable broad component is well correlated with the continuum variation. It consists of a double peaked structure with radial velocities ~+/-1000 km/s relative to the narrow component. A constant component, whose presence is independent of the continuum flux variations, shows only narrow emission lines. The mean, rms, and the averaged over years, observed and difference line profiles of H{beta} and H{alpha} reveal the same double peaked structure. The relative intensity of these peaks changes with time. During 1996, the red peak was the brightest, while in 1998-2002, the blue peak became the brighter one. Their radial velocities vary in the ~(500-1200) km/s range. In 2000-2002 a distinct third peak appeared in the red wing of H{alpha} and H{beta} line profiles. The radial velocity of this feature decreased between 2000 and 2002: from the observed profiles, from ~+(2500-2600) km/s to ~+2000 km/s and is clearly seen on the difference profiles. The fluxes of the various parts of the line profiles are well correlated with each other and also with the continuum flux. The blue and red parts of the line profiles at the same radial velocities vary in an almost identical manner. Shape changes of the different parts of the broad line are not correlated with continuum variations and, apparently, are not related to reverberation effects. Changes of the integral Balmer decrement are, on average, anticorrelated with the continuum flux variations. This is probably due to an increasing role of collisional excitation as the ionizing flux decreases. The behaviour of the Balmer decrement of the various parts of the line profiles was different in 1996-2000 as compared with the 2001 behaviour. Our results favour the formation of the broad Balmer lines in a turbulent accretion disc with large and moving "optically thick" inhomogeneities, capable of reprocessing the central source continuum.
636. Properties of a sample of Seyfert 1 galaxies
ID:
ivo://CDS.VizieR/J/AJ/143/83
Title:
Properties of a sample of Seyfert 1 galaxies
Short Name:
J/AJ/143/83
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a statistical study of a large, homogeneously analyzed sample of narrow-line Seyfert 1 (NLS1) galaxies, accompanied by a comparison sample of broad-line Seyfert 1 (BLS1) galaxies. Optical emission-line and continuum properties are subjected to correlation analyses, in order to identify the main drivers of the correlation space of active galactic nuclei (AGNs), and of NLS1 galaxies in particular. For the first time, we have established the density of the narrow-line region as a key parameter in Eigenvector 1 space, as important as the Eddington ratio L/L_Edd_. This is important because it links the properties of the central engine with the properties of the host galaxy, i.e., the interstellar medium (ISM). We also confirm previously found correlations involving the line width of H{beta} and the strength of the Fe II and [O III]{lambda}5007 emission lines, and we confirm the important role played by L/L_Edd_ in driving the properties of NLS1 galaxies. A spatial correlation analysis shows that large-scale environments of the BLS1 and NLS1 galaxies of our sample are similar. If mergers are rare in our sample, accretion-driven winds, on the one hand, or bar-driven inflows, on the other hand, may account for the strong dependence of Eigenvector 1 on ISM density.
637. Properties of BAL quasars
ID:
ivo://CDS.VizieR/J/MNRAS/469/3163
Title:
Properties of BAL quasars
Short Name:
J/MNRAS/469/3163
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate broad absorption line (BAL) disappearance and emergence using a 470 BAL-quasar sample over <=0.10-5.25 rest-frame years with at least three spectroscopic epochs for each quasar from the Sloan Digital Sky Survey. We identify 14 disappearing BALs over <=1.73-4.62 rest-frame years and 18 emerging BALs over <=1.46-3.66 rest-frame years associated with the CIV{lambda}{lambda}1548,1550 and/or SiIV{lambda}{lambda}1393,1402 doublets, and report on their variability behaviour. BAL quasars in our data set exhibit disappearing/emerging C IV BALs at a rate of 2.3^+0.9^_-0.7_ and 3.0^+1.0^_-0.8_ per cent, respectively, and the frequency for BAL to non-BAL quasar transitions is 1.7^+0.8^_-0.6_ per cent. We detect four re-emerging BALs over <=3.88 rest-frame years on average and three re-disappearing BALs over <=4.15 rest-frame years on average, the first reported cases of these types. We infer BAL lifetimes along the line of sight to be nominally <=100-1000yr using disappearing CIV BALs in our sample. Interpretations of (re-)emerging and (re-)disappearing BALs reveal evidence that collectively supports both transverse-motion and ionization-change scenarios to explain BAL variations. We constrain a nominal CIV/SiIV BAL-outflow location of <=100pc from the central source and a radial size of >=1x10^-7^pc (0.02au) using the ionization-change scenario, and constrain a nominal outflow location of <=0.5pc and a transverse size of ~0.01pc using the transverse-motion scenario. Our findings are consistent with previous work, and provide evidence in support of BALs tracing compact flow geometries with small filling factors.
638. Properties of 1329 extended radio galaxies
ID:
ivo://CDS.VizieR/J/MNRAS/466/4346
Title:
Properties of 1329 extended radio galaxies
Short Name:
J/MNRAS/466/4346
Date:
21 Oct 2021
Publisher:
CDS
Description:
Powerful radio galaxies exist as either compact or extended sources, with the extended sources traditionally classified by their radio morphologies as Fanaroff-Riley (FR) type I and II sources. FRI/FRII and compact radio galaxies have also been classified by their optical spectra into two different types: high excitation (HERG; quasar-mode) and low excitation (LERG; jet-mode). We present a catalogue of visual morphologies for a complete sample of >1000 1.4-GHz-selected extended radio sources from the Sloan Digital Sky Survey. We study the environment and host galaxy properties of FRI/FRII and compact sources, classified into HERG/LERG types, in order to separate and distinguish the factors that drive the radio morphological variations from those responsible for the spectral properties. Comparing FRI LERGs with FRII LERGs at fixed stellar mass and radio luminosity, we show that FRIs typically reside in richer environments and are hosted by smaller galaxies with higher mass surface density; this is consistent with extrinsic effects of jet disruption driving the Fanaroff-Riley (FR) dichotomy. Using matched samples of HERGs and LERGs, we show that HERG host galaxies are more frequently star forming, with more evidence for disc-like structure than LERGs, in accordance with currently favoured models of fundamentally different fuelling mechanisms. Comparing FRI/FRII LERGs with compact LERGs, we find the primary difference is that compact objects typically harbour less massive black holes. This suggests that lower mass black holes may be less efficient at launching stable radio jets, or do so for shorter times. Finally, we investigate rarer sub-classes: wide-angle-tailed, head-tail, FR-hybrid and double-double sources.
639. Properties of IR-bright AGNs
ID:
ivo://CDS.VizieR/J/MNRAS/478/4238
Title:
Properties of IR-bright AGNs
Short Name:
J/MNRAS/478/4238
Date:
10 Dec 2021 00:55:32
Publisher:
CDS
Description:
We report the relationship between the luminosities of active galactic nuclei (AGNs) and the rates of star formation (SF) for a sample of 323 far-infrared (FIR)-detected AGNs. This sample has a redshift range of 0.2<z<2.5, and spans three orders of magnitude in luminosity, L_X_~10^42-45^erg/s. We find that in AGN hosts, the total infrared (IR) luminosity (8-1000um) has a significant AGN contribution (average ~20 per cent), and we suggest using the FIR luminosity (30-1000um) as a more reliable star formation rate (SFR) estimator. We conclude that monochromatic luminosities at 60 and 100um are also good SFR indicators with negligible AGN contributions, being less sensitive than integrated IR luminosities to the shape of the AGN spectral energy distribution (SED), which is uncertain at {lambda}>100um. Significant bivariate L_X_-L_IR_ correlations are found, which remain significant in the combined sample when using residual partial correlation analysis to account for the inherent redshift dependence. No redshift or mass dependence is found for the ratio between SFR and black hole accretion rate (BHAR), which has a mean and scatter of log(SFR/BHAR)=3.1+/-0.5, agreeing with the local mass ratio between supermassive black hole and host galaxies. The large scatter in this ratio and the strong AGN-SF correlation found in these IR-bright AGNs are consistent with the scenario of an AGN-SF dependence on a common gas supply, regardless of the evolutionary model.
640. Properties of the AGN sample
ID:
ivo://CDS.VizieR/J/A+A/646/A96
Title:
Properties of the AGN sample
Short Name:
J/A+A/646/A96
Date:
21 Oct 2021
Publisher:
CDS
Description:
Feedback from active galactic nuclei (AGN) is thought to be key in shaping the life cycle of their host galaxies by regulating star-formation activity. Therefore, to understand the impact of AGN on star formation, it is essential to trace the molecular gas out of which stars form. In this paper we present the first systematic study of the CO properties of AGN hosts at z~=2 for a sample of 27 X-ray selected AGN spanning two orders of magnitude in AGN bolometric luminosity (logL_bol_/(erg/s)=44.7-46.9) by using ALMA Band 3 observations of the CO(3-2) transition (~1" angular resolution). To search for evidence of AGN feedback on the CO properties of the host galaxies, we compared our AGN with a sample of inactive (i.e., non-AGN) galaxies from the PHIBSS survey with similar redshift, stellar masses, and star-formation rates (SFRs). We used the same CO transition as a consistent proxy for the gas mass for the two samples in order to avoid systematics involved when assuming conversion factors (e.g., excitation corrections and CO). By adopting a Bayesian approach to take upper limits into account, we analyzed CO luminosities as a function of stellar masses and SFRs, as well as the ratio L'_CO(3-2)_-M* (a proxy for the gas fraction). The two samples show statistically consistent trends in the L'_CO(3-2)_-L_FIR_ and L'_CO(3-2)_-M* planes. However, there are indications that AGN feature lower CO(3-2) luminosities (0.4-0.7dex) than inactive galaxies at the 2-3 level when we focus on the subset of parameters where the results are better constrained (i.e., L_FIR_~=10^12.2^L_{sun}_ and M*>10^11^M_{sun}_) and on the distribution of the mean log(L'_CO(3-2)_/M*). Therefore, even by conservatively assuming the same excitation factor r31, we would find lower molecular gas masses in AGN, and assuming higher r31 would exacerbate this difference. We interpret our result as a hint of the potential effect of AGN activity (such as radiation and outflows), which may be able to heat, excite, dissociate, and/or deplete the gas reservoir of the host galaxies. Better SFR measurements and deeper CO observations for AGN as well as larger and more uniformly selected samples of both AGN and inactive galaxies are required to confirm whether there is a true difference between the two populations.