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701. AGN selected from an HRC/BHRC sample. II.
ID:
ivo://CDS.VizieR/J/other/Ap/63.166
Title:
AGN selected from an HRC/BHRC sample. II.
Short Name:
J/other/Ap/63.16
Date:
21 Oct 2021
Publisher:
CDS
Description:
This is a detailed spectral classification of 198 candidate active galactic nuclei (AGN) from a joint HRC/BHRC sample consisting of a combination of the HRC (Hamburg-ROSAT) and BHRC (Byurakan-ROSAT) catalogs. These objects have been identified as optical counterparts of ROSAT X-ray sources, but spectra for 198 of them are given in the SDSS without determinations of their spectral classification. They are studied using the SDSS spectra and detailed types of activity are found for them. For a more reliable classification, three diagnostic diagrams have been used, along with direct studies of the spectra. These sources were also identified in other wavelength ranges and their physical parameters have also been calculated.
702. AGNs emission-line from Post-COSTAR
ID:
ivo://CDS.VizieR/J/ApJS/150/165
Title:
AGNs emission-line from Post-COSTAR
Short Name:
J/ApJS/150/165
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present consistent emission-line measurements for active galactic nuclei (AGNs), useful for reliable statistical studies of emission line properties. This paper joins a series including similar measurements of 993 spectra from the Large Bright Quasar Survey and 174 spectra of AGNs obtained from the Faint Object Spectrograph (FOS) on the Hubble Space Telescope (HST) prior to the installation of COSTAR. This time we concentrate on 220 spectra obtained with the FOS after the installation of COSTAR, completing the emission line analysis of all FOS archival spectra. We use the same automated technique as in previous papers, which accounts for Galactic extinction, models blended optical and UV iron emission, includes Galactic and intrinsic absorption lines, and models emission lines using multiple Gaussians. We present UV and optical emission line parameters (equivalent widths, fluxes, FWHM, and line positions) for a large number (28) of emission lines including upper limits for undetected lines. Further scientific analyses will be presented in subsequent papers.
703. AGN Seyfert galaxies and close neighbors
ID:
ivo://CDS.VizieR/J/ApJ/639/37
Title:
AGN Seyfert galaxies and close neighbors
Short Name:
J/ApJ/639/37
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a three-dimensional study of the local (<=100h^-1^kpc) and the large-scale (<=1h^-1^Mpc) environment of the two main types of Seyfert AGN galaxies. For this purpose we use 48 Seyfert 1 galaxies (with redshifts in the range 0.007<=z<=0.036) and 56 Seyfert 2 galaxies (with 0.004<=z<=0.020), located at high galactic latitudes, as well as two control samples of nonactive galaxies having the same morphological, redshift, and diameter size distributions as the corresponding Seyfert samples.
704. AGNs from RXTE 3-20keV All-Sky Survey
ID:
ivo://CDS.VizieR/J/A+A/423/469
Title:
AGNs from RXTE 3-20keV All-Sky Survey
Short Name:
J/A+A/423/469
Date:
21 Oct 2021
Publisher:
CDS
Description:
We compiled a sample of 95 AGNs serendipitously detected in the 3-20keV band at Galactic latitude |b|>10deg during the RXTE slew survey (XSS, Revnivtsev et al., Cat. <J/A+A/418/927>), and utilize it to study the statistical properties of the local population of AGNs, including the X-ray luminosity function and absorption distribution. We find that among low X-ray luminosity (LX<10^43.5^erg/s) AGNs, the ratio of absorbed (characterized by intrinsic absorption in the range 10^22^cm^-2^<NH<10^24^cm^-2^) and unabsorbed (NH<10^22^cm^-2^) objects is 2:1, while this ratio drops to less than 1:5 for higher luminosity AGNs. The summed X-ray output of AGNs with LX>10^41^erg/s estimated here is smaller than the earlier estimated total X-ray volume emissivity in the local Universe, suggesting that a comparable X-ray flux may be produced together by lower luminosity AGNs, non-active galaxies and clusters of galaxies. Finally, we present a sample of 35 AGN candidates, composed of unidentified XSS sources.
705. AGN short time-scale optical variability
ID:
ivo://CDS.VizieR/J/MNRAS/476/2501
Title:
AGN short time-scale optical variability
Short Name:
J/MNRAS/476/2501
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the first short time-scale (~ hours to days) optical variability study of a large sample of active galactic nuclei (AGNs) observed with the Kepler/K2 mission. The sample contains 252 AGN observed over four campaigns with ~30 min cadence selected from the Million Quasar Catalogue with R magnitude <19. We performed time series analysis to determine their variability properties by means of the power spectral densities (PSDs) and applied Monte Carlo techniques to find the best model parameters that fit the observed power spectra. A power-law model is sufficient to describe all the PSDs of our sample. A variety of power-law slopes were found indicating that there is not a universal slope for all AGNs. We find that the rest-frame amplitude variability in the frequency range of 6x10^-6^-10^-4^Hz varies from 1 to 10 per cent with an average of 1.7 per cent. We explore correlations between the variability amplitude and key parameters of the AGN, finding a significant correlation of rest-frame short-term variability amplitude with redshift. We attribute this effect to the known 'bluer when brighter' variability of quasars combined with the fixed bandpass of Kepler data. This study also enables us to distinguish between Seyferts and blazars and confirm AGN candidates. For our study, we have compared results obtained from light curves extracted using different aperture sizes and with and without detrending. We find that limited detrending of the optimal photometric precision light curve is the best approach, although some systematic effects still remain present.
706. AGNs in LSB galaxies
ID:
ivo://CDS.VizieR/J/other/RAA/9.269
Title:
AGNs in LSB galaxies
Short Name:
J/other/RAA/9.26
Date:
21 Oct 2021
Publisher:
CDS
Description:
Active galactic nuclei (AGNs) in low surface brightness galaxies (LSBGs) have received little attention in previous studies. We present a detailed spectral analysis of 194 LSBGs from the Impey et al. (1996, Cat. J/ApJS/105/209) APM LSBG sample which has been observed spectroscopically by the Sloan Digital Sky Survey Data Release 5 (SDSS DR5). Our elaborate spectral analysis enables us to carry out, for the first time, reliable spectral classification of nuclear processes in LSBGs based on the standard emission line diagnostic diagrams in a rigorous way. Star-forming galaxies are common, as found in about 52% of LSBGs.We find that, contrary to some previous claims, the fraction of galaxies that contain AGNs is significantly lower than that found in nearby normal galaxies of high surface brightness. This is qualitatively in line with the finding of Impey et al. This result holds true even within each morphological type from Sa to Sc. LSBGs that have larger central stellar velocity dispersions or larger physical sizes tend to have a higher chance of harboring an AGN. For three AGNs with broad emission lines, the black hole masses estimated from the emission lines are broadly consistent with the well known M-{sigma}* relation established for normal galaxies and AGNs.
707. AGNs in nuclear star clusters
ID:
ivo://CDS.VizieR/J/ApJ/678/116
Title:
AGNs in nuclear star clusters
Short Name:
J/ApJ/678/116
Date:
21 Oct 2021
Publisher:
CDS
Description:
We study galaxies that host both nuclear star clusters and AGNs, implying the presence of a massive black hole. We select a sample of 176 galaxies with previously detected nuclear star clusters that range from ellipticals to late-type spirals. We search for AGNs in this sample using optical spectroscopy and archival radio and X-ray data. We find galaxies of all Hubble types and with a wide range of masses (10^9^-10^11^M_{sun}_) hosting both AGNs and nuclear star clusters. From the optical spectra, we classify 10% of the galaxies as AGN and an additional 15% as composite, indicating a mix of AGN and star formation spectra. The fraction of nucleated galaxies with AGNs increases strongly as a function of galaxy and nuclear star cluster mass. For galaxies with both a nuclear star cluster and a black hole, we find that the masses of these two objects are quite similar. However, nondetections of black holes in Local Group nuclear star clusters show that not all clusters host black holes of similar masses. We discuss the implications of our results for the formation of nuclear star clusters and massive black holes.
708. AGNs in submm-selected Lockman Hole galaxies
ID:
ivo://CDS.VizieR/J/A+A/514/A10
Title:
AGNs in submm-selected Lockman Hole galaxies
Short Name:
J/A+A/514/A10
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a comparison of the SCUBA half degree extragalactic survey (SHADES) at 450{mu}m, 850{mu}m and 1100{mu}m with deep guaranteed time 15{mu}m AKARI FU-HYU survey data and Spitzer guaranteed time data at 3.6-24{mu}m in the Lockman hole east. The AKARI data was analysed using bespoke software based in part on the drizzling and minimum-variance matched filtering developed for SHADES, and was cross-calibrated against ISO fluxes.
709. AGNs in the Extended Groth Strip Survey
ID:
ivo://CDS.VizieR/J/AJ/137/179
Title:
AGNs in the Extended Groth Strip Survey
Short Name:
J/AJ/137/179
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have employed a reliable technique of classification of active galactic nuclei (AGNs) based on the fit of well sampled spectral energy distributions (SEDs) with a complete set of AGN and starburst galaxy templates. We have compiled UV, optical, and IR data for a sample of 116 AGNs originally selected for their X-ray and mid-IR emissions (96 with single detections and 20 with double optical counterparts). This is the most complete compilation of multiwavelength data for such a large sample of AGN in the Extended Groth Strip. Through these SEDs, we are able to obtain highly reliable photometric redshifts and to distinguish between pure and host-dominated AGNs.
710. AGNs in the MIR using AllWISE data
ID:
ivo://CDS.VizieR/J/ApJS/221/12
Title:
AGNs in the MIR using AllWISE data
Short Name:
J/ApJS/221/12
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an all-sky sample of ~1.4 million active galactic nuclei (AGNs) meeting a two-color infrared photometric selection criteria for AGNs as applied to sources from the Wide-field Infrared Survey Explorer final catalog release (AllWISE). We assess the spatial distribution and optical properties of our sample and find that the results are consistent with expectations for AGNs. These sources have a mean density of ~38 AGNs per square degree on the sky, and their apparent magnitude distribution peaks at g~20, extending to objects as faint as g~26. We test the AGN selection criteria against a large sample of optically identified stars and determine the "leakage" (that is, the probability that a star detected in an optical survey will be misidentified as a quasi-stellar object (QSO) in our sample) rate to be <=4.0x10^-5^. We conclude that our sample contains almost no optically identified stars (<=0.041%), making this sample highly promising for future celestial reference frame work as it significantly increases the number of all-sky, compact extragalactic objects. We further compare our sample to catalogs of known AGNs/QSOs and find a completeness value of >~84% (that is, the probability of correctly identifying a known AGN/QSO is at least 84%) for AGNs brighter than a limiting magnitude of R<~19. Our sample includes approximately 1.1 million previously uncataloged AGNs.

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