scholarly journals Multi-wavelength studies of the statistical properties of active galaxies using Big Data

2016 ◽  
Vol 12 (S325) ◽  
pp. 32-38
Author(s):  
A. M. Mickaelian ◽  
H. V. Abrahamyan ◽  
M. V. Gyulzadyan ◽  
G. A. Mikayelyan ◽  
G. M. Paronyan
Keyword(s):  
Big Data ◽  
Active Galaxies ◽  
Radio Sources ◽  
Statistical Research ◽  
Homogeneous Sample ◽  
X Ray ◽  
Multi Wavelength ◽  
Statistical Studies ◽  
Spectroscopic Database ◽  
Variable Radio

AbstractStatistical studies of active galaxies (both AGN and Starburst) using large multi-wavelength data are presented, including new studies of Markarian galaxies, large sample of IR galaxies, variable radio sources, and large homogeneous sample of X-ray selected AGN. Markarian survey (the First Byurakan Survey) was digitized and the DFBS database was created, as the biggest spectroscopic database by the number of objects involved ( ~ 20 million). This database provides both 2D images and 1D spectra. We have carried out a number of projects aimed at revealing and multi-wavelength studies of active galaxies among optical, X-ray, IR and radio sources. Thousands of X-ray sources were identified from ROSAT, including many AGN (52% among all identified sources). IRAS PSC/FSC sources were studied having accurate positions from WISE and a large extragalactic sample was created for further search for AGNs. The fraction of active galaxies among IR-selected galaxies was estimated as 24%. Variable radio sources at 1.4 GHz were revealed by cross-correlation of NVSS and FIRST catalogues using the method introduced by us for optical variability. Radio-X-ray sources were revealed from NVSS and ROSAT for detection of new active galaxies. Big Data in astronomy is described that provide new possibilities for statistical research of active galaxies and other objects.

Studying the Flux Density of Bright Active Galaxies at Different Spectral Bands

2019 ◽  
Vol 16 (1(Suppl.)) ◽  
pp. 0230
Author(s):  
Rashed Et al.
Keyword(s):  
Flux Density ◽  
Galactic Nuclei ◽  
Absolute Magnitude ◽  
Active Galaxies ◽  
X Ray ◽  
Spectral Bands ◽  
Sky Survey ◽  
Multi Wavelength ◽  
Statistical Studies ◽  
Density Ratios

Statistical studies are reported in this article for an active galactic nuclei sample of different type of active galaxies Seyferts 1, Seyferts 2, and Quasars. These sources have been selected from a Catalogue for bright X-ray galaxies. The name of this index is ROSAT Bright Source Catalogue (RBSC) and the NRAO VLA Sky Survey (NVSS). In this research, multi-wavelength observational bands Radio at 1.4 GHz, Optical at 4400 A0, and X-ray at energy 0.1-2.4 KeV have been adopted in this study. The behavior of flux density ratios has been studied ,  with respect to the absolute magnitude . Furthermore, the Seyfert1 and Seyfert 2 objects are combined in one group and the QSOs are collectest in another group. Also, it has been found that the ratios , are increasing towards fainter optical absolute magnitude especially in Quasars.

scholarly journals Studying the Flux Density of Bright Active Galaxies at Different Spectral Bands

2019 ◽  
Vol 16 (1) ◽  
pp. 0230
Author(s):  
Rashed Et al.
Keyword(s):  
Flux Density ◽  
Galactic Nuclei ◽  
Absolute Magnitude ◽  
Active Galaxies ◽  
X Ray ◽  
Spectral Bands ◽  
Sky Survey ◽  
Multi Wavelength ◽  
Statistical Studies ◽  
Density Ratios

Statistical studies are reported in this article for an active galactic nuclei sample of different type of active galaxies Seyferts 1, Seyferts 2, and Quasars. These sources have been selected from a Catalogue for bright X-ray galaxies. The name of this index is ROSAT Bright Source Catalogue (RBSC) and the NRAO VLA Sky Survey (NVSS). In this research, multi-wavelength observational bands Radio at 1.4 GHz, Optical at 4400 A0, and X-ray at energy 0.1-2.4 KeV have been adopted in this study. The behavior of flux density ratios has been studied ,  with respect to the absolute magnitude . Furthermore, the Seyfert1 and Seyfert 2 objects are combined in one group and the QSOs are collectest in another group. Also, it has been found that the ratios , are increasing towards fainter optical absolute magnitude especially in Quasars.

Radio Observations of the Einstein Deep X-ray Field in Pavo

1990 ◽  
Vol 8 (04) ◽  
pp. 348-352 ◽  
Author(s):  
T. R. Bedding ◽  
A. J. Turtle
Keyword(s):  
Flux Density ◽  
Radio Sources ◽  
Radio Observations ◽  
X Ray ◽  
Object A ◽  
Multi Wavelength ◽  
Radio Map ◽  
Einstein Observatory

AbstractThe most sensitive X-ray survey available is a deep exposure made by theEinstein Observatoryof a 40 arcmin field in the southern constellation of Pavo. This survey revealed 33 X-ray sources, most of which were optically identified with quasars. Here, we report radio observations of the Pavo region at 843 MHz made with the Molonglo Observatory Synthesis Telescope. Eight overlapping fields were combined to produce the most sensitive radio map of the region to date, revealing 33 radio sources above a flux density of 2.4 mJy. Only one of these radio sources corresponded to an X-ray object: a quasar atz= 1.13. We also used the Parkes-Tidbinbilla Interferometer, at 2.29 GHz and 8.41 GHz, to observe some of the stronger radio sources.From these multi-wavelength observations of the Pavo field it is apparent that, to the sensitivity of the surveys involved, (i) there is little correlation between X-ray and radio detections, and (ii) most of the X-ray sources have optical counterparts while few of the radio ones do, and (iii) there is some confirmation that X-ray emission is higher for objects with flat radio spectra (i.e., a dominant core) than for steep spectrum sources.

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

2021 ◽  
Vol 7 ◽  
Author(s):  
A. M. Mickaelian ◽  
H. V. Abrahamyan ◽  
G. M. Paronyan ◽  
G. A. Mikayelyan
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Radio Sources ◽  
Spectral Classification ◽  
X Ray ◽  
Activity Types ◽  
Larger Sample ◽  
Variable Radio ◽  
Fine Classification

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.

scholarly journals Halo concentration, galaxy red fraction, and gas properties of optically defined merging clusters†

2019 ◽  
Vol 71 (4) ◽  
Author(s):  
Nobuhiro Okabe ◽  
Masamune Oguri ◽  
Hiroki Akamatsu ◽  
Akinari Hamabata ◽  
Atsushi J Nishizawa ◽  
...  
Keyword(s):  
Brightness Distribution ◽  
Single Peak ◽  
Homogeneous Sample ◽  
X Ray ◽  
Mass Distributions ◽  
Whole Process ◽  
Multi Wavelength ◽  
Strategic Program ◽  
Cluster Mergers ◽  
Red Galaxies

Abstract We present multi-wavelength studies of optically defined merging clusters, based on the Hyper Suprime-Cam Subaru Strategic Program. Luminous red galaxies, tracing cluster mass distributions, enable us to identify cluster subhalos at various merging stages, and thus make a homogeneous sample of cluster mergers that is unbiased with respect to the merger boost of the intracluster medium (ICM). We define, using a peak-finding method, merging clusters with multiple peaks and single clusters with single peaks from the CAMIRA cluster catalog. Stacked weak-lensing analysis indicates that our sample of merging clusters is categorized into major mergers. The average halo concentration for the merging clusters is ∼70% smaller than that of the single-peak clusters, which agrees well with predictions of numerical simulations. The spatial distribution of subhalos is less centrally concentrated than the mass distribution of the main halo. The fractions of red galaxies in the merging clusters are not higher than those of the single-peak clusters. We find a signature of the merger boost of the ICM from the stacked Planck Sunyaev–Zel’dovich effect and ROSAT X-ray luminosity, but not in optical richness. The stacked X-ray surface brightness distribution, aligned with the main subhalo pairs of low-redshift and massive clusters, shows that the central gas core is elongated along the merger axis, and overall gas distribution is misaligned by ∼60°. The homogeneous, unbiased sample of cluster mergers and multi-wavelength follow-up studies provide a unique opportunity to make a complete picture of merger physics over the whole process.

scholarly journals Disentangling the AGN and Star-forming Contribution to the Sub-mJy Radio Counts

2006 ◽  
Vol 2 (S235) ◽  
pp. 333-333
Author(s):  
Nick Seymour ◽  
D. Moss ◽  
T. Dwelly ◽  
I. McHardy ◽  
M. Page ◽  
...  
Keyword(s):  
Optical Spectra ◽  
Radio Sources ◽  
Radio Flux ◽  
True Nature ◽  
X Ray ◽  
Star Forming ◽  
Lack Of Information ◽  
Multi Wavelength ◽  
The Many ◽  
First Time

AbstractThe true nature of the faint radio population remains elusive despite the many observations of the “sub-mJy” bump over the last two decades. This lack of information is largely due to the faint magnitudes of the optical counterparts to the radio sources. There are strong theoretical reasons (and a few observational ones) to believe that this rise in the counts is due to the emergence of a rapidly evolving star-forming population. Now, for the first time, we are able to separate the AGN and star-forming populations below 1mJy using a combination of multi-wavelength data from Spitzer, GMRT, MERLIN, CFHT, Keck, UKIRT, Subaru, Chandra and XMM-Newton. The many discriminators between these emission mechanisms include MIR colours, MIR/radio flux ratios, X-ray luminosities/spectra, optical spectra, radio morphologies and radio spectra. We can now derive the source counts separately for AGN and star-forming galaxies confirming that the latter population rise sharply at faint flux densities.

scholarly journals Large homogeneous sample of X-ray selected AGN and its study

2015 ◽  
Vol 11 (A29B) ◽  
pp. 91-91
Author(s):  
Areg Mickaelian ◽  
Gurgen Paronyan ◽  
Hayk Abrahamyan
Keyword(s):  
Homogeneous Sample ◽  
X Ray ◽  
Statistical Studies ◽  
Optical Identifications

AbstractThe combined catalogue of AGN selected from optical identifications of X-ray sources based on Hamburg–ROSAT and Byurakan–Hamburg–ROSAT catalogues is a homogeneous sample for statistical studies. Optically identified X-ray sources from ROSAT BSC and FSC are included, 4253 X-ray selected AGN in total. We carried out classification for 210 of these candidate sources based on available SDSS spectra and enlarged the sample of confirmed AGN. Statistical investigations of the sample were also carried out. Multiwavelength SEDs have also been constructed to link them to classifications.

Relativistic astrophysics and cosmology

2019 ◽  
pp. 244-291
Author(s):  
Malcolm S. Longair
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
High Energy ◽  
Active Galaxies ◽  
Relativistic Astrophysics ◽  
Radio Sources ◽  
X Ray ◽  
Binary Black Hole ◽  
Wide Range ◽  
New Challenges

Although relativistic astrophysics began in the 1930s with study of supernovae and neutron stars, it was only three decades later that the discovery of extragalactic radio sources, quasars and pulsars marked the emergence of special and general relativity as essential tools of the high energy astrophysicist. X-ray and γ-ray astronomy provided many new insights, culminating in the discovery of γ-ray bursts at cosmological distances in 1997. Supermassive black holes in active galactic nuclei provided major new challenges for theorists and observers alike, revealing many remarkable relativistic phenomena, such as superluminal motions observed in some of the most active galaxies. Einstein’s prediction of gravitational waves of 1916 was substantiated exactly 100 years later with their discovery in coalescing binary black hole systems by the LIGO project. These remarkable discoveries, mostly in the non-optical wavebands, brought a wide range of physicists into the astronomical and cosmological communities.

scholarly journals Radio Properties of AGN

2013 ◽  
Vol 9 (S304) ◽  
pp. 102-103 ◽  
Author(s):  
Hayk V. Abrahamyan ◽  
Areg M. Mickaelian
Keyword(s):  
Physical Properties ◽  
Cross Correlation ◽  
Active Galaxies ◽  
Radio Sources ◽  
Positional Accuracy ◽  
Homogeneous Sample ◽  
Radio Detection ◽  
Luminosity Functions ◽  
Activity Types

AbstractTo study the radio properties of AGN, we cross-correlate and investigate Veron-Cetty & Veron catalog of QSOs and Active Galaxies (v.13, 2010) with a number of radio catalogs: NVSS, FIRST, GB6, 87GB, SUMSS, WISH, WENSS, and 7C. This catalog contains 168,940 objects with positional accuracy of mostly 1 arcsec, though many positions have larger errors. We use new cross-correlation software based on accuracy of each object independently. In this software we take into account errors for each source and take identifications with errors within 3 sigma. Altogether, we find ~16,000 AGN having radio detection in any of the listed catalogs. Using all data from radio catalogs, we derive a homogeneous sample of radio AGN. The sample allows accomplish several tasks, including study of the distribution of radio sources by activity types, differences in physical properties of radio-loud and radio-quiet AGN, luminosity functions for various types of radio AGN, study of the q parameter by AGN types and its evolution, etc.

scholarly journals Where the active galaxies live: a panchromatic view of radio-AGN in the AKARI-NEP field

2012 ◽  
Vol 8 (S295) ◽  
pp. 270-270
Author(s):  
Marios Karouzos ◽  
Myungshin Im ◽  
Markos Trichas ◽  
Keyword(s):  
Star Formation ◽  
Active Galaxies ◽  
Host Galaxy ◽  
Radio Sources ◽  
Relative Importance ◽  
Host Galaxies ◽  
Star Formation Activity ◽  
Multi Wavelength

AbstractWe study the host galaxy properties of radio sources in the AKARI-North Ecliptic Pole (NEP) field, using an ensemble of multi-wavelength datasets. We identify both radio-loud and radio-quiet AGN and study their host galaxy properties by means of SED fitting. We investigate the relative importance of nuclear and star-formation activity in radio-AGN and assess the role of radio-AGN as efficient quenchers of star-formation in their host galaxies.

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