- ID:
- ivo://CDS.VizieR/J/ApJ/835/223
- Title:
- A catalog of nearby galaxies with Chandra obs.
- Short Name:
- J/ApJ/835/223
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We searched the public archive of the Chandra X-ray Observatory as of 2016 March and assembled a sample of 719 galaxies within 50Mpc with available Advanced CCD Imaging Spectrometer observations. By cross-correlation with the optical or near-infrared nuclei of these galaxies, 314 of them are identified to have an X-ray active galactic nucleus (AGN). The majority of them are low-luminosity AGNs and are unlikely X-ray binaries based upon their spatial distribution and luminosity functions. The AGN fraction is around 60% for elliptical galaxies and early-type spirals, but drops to roughly 20% for Sc and later types, consistent with previous findings in the optical. However, the X-ray survey is more powerful in finding weak AGNs, especially from regions with active star formation that may mask the optical AGN signature. For example, 31% of the H II nuclei are found to harbor an X-ray AGN. For most objects, a single power-law model subject to interstellar absorption is adequate to fit the spectrum, and the typical photon index is found to be around 1.8. For galaxies with a non-detection, their stacked Chandra image shows an X-ray excess with a luminosity of a few times 10^37^erg/s on average around the nuclear region, possibly composed of faint X-ray binaries. This paper reports on the technique and results of the survey; in-depth analysis and discussion of the results will be reported in forthcoming papers.
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- ID:
- ivo://CDS.VizieR/J/ApJ/857/27
- Title:
- A catalog of post-starburst QSOs from SDSS-DR7Q
- Short Name:
- J/ApJ/857/27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of nearby (z<=0.5) quasars with significant features of post-starburst stellar populations in their optical spectra: so-called post-starburst quasars, or PSQs. After carefully decomposing spectra from the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) Quasar Catalog into quasar and host-galaxy components, we derive a sample of 208 PSQs. Their host-galaxy components have strong H{delta} absorption (EW>=6{AA}) indicating a significant contribution of an intermediate-aged stellar population formed in a burst of star formation within the past 1Gyr, which makes them potentially useful for studying the co-evolution of supermassive black holes and their host galaxies.
- ID:
- ivo://CDS.VizieR/J/other/ChA+A/32.351
- Title:
- Accretion rate distributions of AGNs
- Short Name:
- J/other/ChA+A/32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The redshift, central black hole mass and accretion rate are important parameters when studying the AGN evolution. The central black hole masses for 172 quasars and Seyfert galaxies are calculated in this paper using the reverberation mapping method. The distributions of central black hole masses, redshifts and the Eddington accretion rates are analyzed, to verify the transition from the quasar to the Seyfert galaxy in the course of evolution.
- ID:
- ivo://CDS.VizieR/J/ApJ/733/60
- Title:
- Accretion rate of AGNs from COSMOS surveys
- Short Name:
- J/ApJ/733/60
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We show how accretion rate governs the physical properties of a sample of unobscured broad-line, narrow-line, and lineless active galactic nuclei (AGNs). We avoid the systematic errors plaguing previous studies of AGN accretion rates by using accurate intrinsic accretion luminosities (Lint) from well-sampled multiwavelength spectral energy distributions from the Cosmic Evolution Survey, and accurate black hole masses derived from virial scaling relations (for broad-line AGNs) or host-AGN relations (for narrow-line and lineless AGNs).
- ID:
- ivo://CDS.VizieR/J/A+AS/147/169
- Title:
- Accurate positions of 2978 SBS objects
- Short Name:
- J/A+AS/147/169
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Optical positions of 2978 objects listed in the Second Byurakan Survey (SBS) were obtained using the Digitized Sky Survey (DSS), and are given with an rms un certainty ~1 arcsec in each coordinate.
- ID:
- ivo://CDS.VizieR/J/ApJS/243/21
- Title:
- A complete sample of broad-line AGN from SDSS-DR7
- Short Name:
- J/ApJS/243/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new, complete sample of 14584 broad-line active galactic nuclei (AGNs) at z<0.35 is presented, which are uncovered homogeneously from the complete database of galaxies and quasars observed spectroscopically in the Sloan Digital Sky Survey Seventh Data Release. The stellar continuum is properly removed for each spectrum with significant host absorption line features, and careful analyses of the emission line spectra, particularly in the H{alpha} and H{beta} wavebands, are carried out. The broad Balmer emission line, particularly H{alpha}, is used to indicate the presence of an AGN. The broad H{alpha} lines have luminosities in a range of 10^38.5^-10^44.3^erg/s, and line widths (FWHMs) of 500-34000km/s. The virial black hole masses, estimated from the broad-line measurements, span a range of 10^5.1^-10^10.3^M_{sun}_, and the Eddington ratios vary from -3.3 to 1.3 in logarithmic scale. Other quantities such as multiwavelength photometric properties and flags denoting peculiar line profiles are also included in this catalog. We describe the construction of this catalog and briefly discuss its properties. The catalog is publicly available online. This homogeneously selected AGN catalog, along with the accurately measured spectral parameters, provides the most updated, largest AGN sample data, which will enable further comprehensive investigations of the properties of the AGN population in the low-redshift universe.
- ID:
- ivo://CDS.VizieR/J/MNRAS/466/2879
- Title:
- Active galactic nuclei from HeII
- Short Name:
- J/MNRAS/466/2879
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to perform a more complete census of active galactic nuclei (AGN) in the local Universe, we investigate the use of the HeII {lambda}4685 emission line diagnostic diagram by Shirazi & Brinchmann (2012, Cat. J/MNRAS/421/1043) in addition to the standard methods based on other optical emission lines. The HeII-based diagnostics is more sensitive to AGN ionization in the presence of strong star formation than conventional line diagnostics. We survey a magnitude-limited sample of 63915 galaxies from the Sloan Digital Sky Survey Data Release 7 at 0.02<z<0.05 and use both the conventional BPT emission line diagnostic diagrams, as well as the HeII diagram to identify AGN. In this sample, 1075 galaxies are selected as AGN using the BPT diagram, while additional 234 galaxies are identified as AGN using the HeII diagnostic diagram, representing a 22 per cent increase of AGN in the parent galaxy sample. We explore the host galaxy properties of these new HeII-selected AGN candidates and find that they are most common in star-forming galaxies on the blue cloud and on the main sequence where ionization from star formation is most likely to mask AGN emission in the BPT lines. We note in particular a high He II AGN fraction in galaxies above the high-mass end of the main sequence where quenching is expected to occur. We use archival Chandra observations to confirm the AGN nature of candidates selected through He II-based diagnostic. Finally, we discuss how this technique can help inform galaxy/black hole coevolution scenarios.
- ID:
- ivo://CDS.VizieR/J/AZh/79/963
- Title:
- Active radio galaxies in cluster A569
- Short Name:
- J/AZh/79/963
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The nature of bright radio sources with known radio spectra in the direction of the nearby cluster of galaxies A569 (z=0.0193) is investigated. The optical identifications of the sources were provided. 45% of these radio sources are associated with compact galaxies. A substantial fraction of these galaxies have active nuclei. Some of them have radio halos.
- ID:
- ivo://CDS.VizieR/J/A+A/552/A135
- Title:
- Activity of the Seyfert galaxy neighbours
- Short Name:
- J/A+A/552/A135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a follow-up study of a series of papers concerning the role of close interactions as a possible triggering mechanism of AGN activity. We have already studied the close (<100kpc/h) and the large-scale (<1Mpc/h) environment of a local sample of Sy1, Sy2, and bright IRAS galaxies (BIRG) and of their respective control samples. The results led us to the conclusion that a close encounter appears capable of activating a sequence where an absorption line galaxy (ALG) galaxy first becomes a starburst, then a Sy2, and finally a Sy1. Here we investigate the activity of neighbouring galaxies of different types of AGN, since both galaxies of an interacting pair should be affected. To this end we present the optical spectroscopy and X-ray imaging of 30 neighbouring galaxies around two local (z<0.034) samples of 10 Sy1 and 13 Sy2 galaxies. Although this is a pilot study of a small sample, various interesting trends have been discovered that imply physical mechanisms that may lead to different Seyfert types. Based on the optical spectroscopy we find that more than 70% of all neighbouring galaxies exhibit star forming and/or nuclear activity (namely recent star formation and/or AGN), while an additional X-ray analysis showed that this percentage might be significantly higher. Furthermore, we find a statistically significant correlation, at a 99.9% level, between the value of the neighbour's [OIII]/H{beta} ratio and the activity type of the central active galaxy, i.e. the neighbours of Sy2 galaxies are systematically more ionized than the neighbours of Sy1s. This result, in combination with trends found using the Equivalent Width of the H{alpha} emission line and the stellar population synthesis code STARLIGHT, indicate differences in the stellar mass, metallicity, and star formation history between the samples. Our results point towards a link between close galaxy interactions and activity and also provide more clues regarding the possible evolutionary sequence inferred by our previous studies.
- ID:
- ivo://CDS.VizieR/J/MNRAS/403/1474
- Title:
- Activity of 70um-selected galaxies
- Short Name:
- J/MNRAS/403/1474
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first active galactic nuclei (AGN) census in a sample of 61 galaxies selected at 70um, a wavelength which should strongly favour the detection of star-forming systems. For the purpose of this study, we take advantage of deep Chandra X-ray and Spitzer infrared (3.6-160um) data, as well as optical spectroscopy and photometry from the Deep Extragalactic Evolutionary Probe 2 (DEEP 2) survey for the Extended Groth Strip (EGS) field, as part of the All-Wavelength Extended Groth Strip International Survey. We investigate spectral line diagnostics ([OIII]/H {beta} and [NeIII]/[OII] ratios, H{delta} Balmer absorption line equivalent widths and the strength of the 4000{AA} break), X-ray luminosities and spectral energy distributions (SEDs).
