Activity Types of Galaxies Selected from HRC/BHRC Sample

et al. 2020

ComBAO

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We present surveys and related studies of active galaxies carried out at the Byurakan Astrophysical Observatory (BAO). This was one of the main research subjects at BAO during many years, since mid-1950s, when Viktor Ambartsumian suggested the hypothesis of the activity of the galactic nuclei. A number of surveys and searches for Active Galactic Nuclei (AGN) and other active galaxies were accomplished during 1960s-1980s. Since mid-1990s, our research group carried out new surveys and studies of active galaxies based on the First Byurakan Survey (FBS or Markarian Survey) and then a number of others. Here we also present the recent results of studies on active galaxies (both AGN and Starbursts) by the Extragalactic group of the Byurakan Astrophysical Observatory (BAO) Research Department “Astronomical Surveys”. These studies are characterized by multiwavelength approach to statistical analysis of large amount of data obtained in different wavelengths; from X-ray to radio. A fine classification scheme for active galaxies has also been suggested.

Section: Discussionmentioning

confidence: 99%

Section: Byurakan Surveys For Active Galaxiesmentioning

confidence: 99%

Surveys for active galaxies: discovery and studies

et al. 2020

ComBAO

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“…• Study of SDSS spectra of 371 optical identifications of HRC/BHRC Sample ROSAT X-ray sources (Paronyan et al 2018(Paronyan et al , 2019a. These sources were also identified in other wavelength ranges and some of their parameters were calculated.…”

Section: Discussionmentioning

confidence: 99%

“…Activity Types of Galaxies Selected from HRC/BHRC Sample (Paronyan et al 2018(Paronyan et al , 2019a In this study we carry out detailed spectral classification of 371 (173+198) AGN candidates from the Joint HRC/BHRC sample, which is a combination of HRC (Hamburg-ROSAT Catalogue) and BHRC (Byurakan-Hamburg-ROSAT Catalogue). These objects were revealed as optical counterparts for ROSAT X-ray sources; however, spectra for 371 of them are given in SDSS without definite spectral classification.…”

Section: Introductionmentioning

confidence: 99%

Studies of Active Galaxies in Byurakan: Recent Results

et al. 2019

ComBAO

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We present the recent results of studies on active galaxies (both AGN and Starbursts) by the Extragalactic group of Byurakan Astrophysical Observatory (BAO) Research Department “Astronomical Surveys”. The research has been carried out in 2017-2019 and the results are published in 2018-2019. These studies are characterized by multiwavelength approach to statistical analysis of large amount of data obtained in different wavelengths; from X-ray to radio. Results on HRC/BHRC sample objects (optical identifications of ROSAT X-ray sources), studies of Markarian galaxies in UV and multiwavelength SEDs, abundance and star formation determinations in Mrk galaxies from SDSS spectra, revised optical classification of “LINERs”, study and classification of SDSS spectra for Byurakan-IRAS Galaxies, summary of observations and study of Byurakan-IRAS Galaxies (BIG objects), discovery of new bright ULIRGs from the IRAS PSC/FSC Combined Catalogue and their spectral classification, radio variable sources at 1400 MHz and their optical variability, classification of BZCAT objects having uncertain types (BZU objects), and optical variability of blazars are presented.

“…In our recent papers (Abrahamyan et al, 2018a;Abrahamyan et al, 2018b;Mikayelyan et al, 2018;Paronyan et al, 2018;Abrahamyan et al, 2019a;Paronyan et al, 2019) we have introduced and developed fine classification of active galaxies to have better understanding of the detailed spectral features between the subclasses. In this paper we use objects provided by Abrahamyan et al (2018b), where 6,301 sources are listed extracted from the comparison of NRAO VLA Sky Survey (NVSS) (Condon et al, 1998) and Faint Images of the Radio Sky at Twenty cm (FIRST) (Helfand et al, 2015) radio catalogues.…”

Section: The Sample Of Studied Objectsmentioning

confidence: 99%

Fine Classification of QSOs and Seyferts for Activity Types Based on SDSS Spectroscopy

Front. Astron. Space Sci.

et al. 2021

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Using the SDSS spectroscopy, we have carried out fine optical spectral classification for activity types for 710 AGN candidates. These objects come from a larger sample of some 2,500 candidate AGN using pre-selection by various samples; bright objects of the Catalog of Quasars and Active Galactic Nuclei, AGN candidates among X-ray sources, optically variable radio sources, IRAS extragalactic objects, etc. A number of papers have been published with the results of this spectral classification. More than 800 QSOs have been identified and classified, including 710 QSOs, Seyferts and Composites. The fine classification shows that many QSOs show the same features as Seyferts, i.e., subtypes between S1 and S2 (S1.2, S1.5, S1.8 and S1.9). We have introduced subtypes for the QSOs: QSO1.2, QSO1.5, QSO1.8, QSO1.9, though the last subtype does not appear in SDSS wavelength range due to mostly highly redshifted Hα (the main line for identification of the 1.9 subtype). Thus, independent of the luminosity (which serves as a separator between QSOs and Seyferts), AGN show the same features. We also have classified many objects as Composites, spectra having composite characteristics between Sy and LINERs, Sy and HII or LINERs and HII; in some cases all three characteristics appear together resulting as Sy/LINER/HII subtype. The QSOs subtypes together with Seyfert ones allow to follow AGN properties along larger redshift range expanding our knowledge on the evolution of AGN to more distant Universe represented by QSOs.