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O. V. Verkhodanov

Publications and source records attributed to O. V. Verkhodanov.

47 records · Page 3Linked to original sources
arXiv2000

Radio identification of decametric sources. I. Catalogue

We describe a method of plotting continuous spectra for radio sources on the basis of entries of various source catalogues in comparatively large error boxes around a given sky position. Sources from the UTR-2 catalogue (Braude et al., 1978, 1979, 1981, 1985, 1994), observed at decametric wavelengths (10--25 MHz) with an antenna beam of about 40', were cross-identified with entries from other radio catalogues at higher frequencies. Using the CATS database we extracted all sources within 40' around UTR positions to find candidate identifications. The spectrum for each source was fitted with a set of curves using the least squares method to find the best fit. We preferentially selected radio counterparts whose radio spectrum extrapolated to low frequencies matched the UTR decametric flux densities, and whose coordinates were close to the gravity centre of UTR positions. Among all 1822 sources in the UTR catalogue we found about 350 sources to be blends of two or more sources. As the most probable true coordinates of the radio counterparts we used positions from the FIRST, NVSS, TXS, GB6, or PMN catalogues. Using low-frequency sources (26, 38, 85 MHz) from CATS we checked the reliability of some of our identifications. We show examples `of the above methods, including raw and ``cleaned'' spectra. Identifications with objects from optical, X-ray and infrared catalogues, as well as a subsample of UTR sources with ultra-steep spectrum are presented.

astro-ph↗
arXiv2000

RATAN-600 - VLA - BTA-6m ("BIG TRIO") Project: multicolour studying of distant radio galaxies

Powerful radio galaxies belong to the population of massive stellar systems that can be picked at high redshifts. With measured redshift, morphology and age determination these objects can help greatly in understanding of the way of formation and evolution of giant elliptical galaxies with massive Black Holes in the Early Universe. We presents some recent results of study of the sample of 105 faint steep spectrum radio sources from RATAN-600 RC catalogue. All the objects has been mapped with the VLA and optical identification have been carried out with the 6m BTA telescope. Using multicolour CCD photometry in B,V,R_c,I_c bands photometric redshift and age of stellar population are estimated for a subsample of 50 FRII and CSS radio galaxies. RC J0105+0501 is a very probable candidate for radio galaxy at z ~ 3.5. Distribution of objects on colour-colour and magnitude-redshift diagrams shows a rough agreement with expectations of theoretical models of SED evolution for giant elliptical galaxies. On the [m_R - z_{phot}] diagram two populations of faint (m_R = 22^m-24^m) radio galaxies are possibly revealed. The first population at z~ 1 consists of mainly old (a half with age >= 5 Gyr) and large (LAS~20") objects, the second one at z = 1.5 - 3.5 includes both younger (<= 3 Gyr) and smaller (LAS ~ 5") objects. There are 12 more faint or still undetected (m_R >= 24.5^m) sources in the sample which may presumably be a very distant radio galaxies (z>3.5) or intermediate redshift old or dusty ones.

astro-ph↗
arXiv2000

Radio-optical identification of very-steep spectrum radio sources from the UTR-2 catalogue

We used radio source catalogues accessible from the CATS database (http://cats.sao.ru) to establish radio continuum spectra for decametric radio sources in the UTR-2 catalogue (Braude et al., 1978--1994). From these, we select a sample of 23 sources with ultra steep radio spectra (α<=-1.2, S ~ ν^α) and present accurate positions and sizes from FIRST and NVSS. The search for optical counterparts from the APM (object) and DSS (image) databases, as well as infrared and X-ray identifications of these UTR sources are in progress.

astro-ph↗
arXiv1999

RC J1148+0455 identification: gravitational lens or group of galaxies ?

The structure of the radio source RC B1146+052 of the ``Cold'' catalogue is investigated by data of the MIT-GB-VLA survey at 4850 MHz. This source belongs to the steep spectrum radio sources subsample of the RC catalogue. Its spectral index is $α$ = -1.04. The optical image of this source obtained with 6m telescope is analysed. The radio source center is situated in a group of 8 galaxies of about 24$^m$ in the R-filter. The possible explanations of the complex structure of radio components are considered.

astro-ph↗
arXiv1999

The software system "Evolution of radio galaxies"

The project of the informational system creation on the problem of evolution of radio galaxies is described. This system, being developed at present, will allow a user to operate with simulated curves of spectral energy distributions (SED) and to estimate ages and redshifts by photometrical data. Authors use SEDs of several models (GISSEL'96 (Bruzual, Charlot, 1996), PEGASE (Fioc, Rocca-Volmerange, 1996) and Poggianti(1996)) for different types of galaxies. Planned modes of access, formats of output result and additional functions are described.

astro-ph↗
arXiv1999

The problem of identifying decametric sources

We describe a method to construct continuum spectra for radio sources on the basis of entries from various source catalogues in comparatively large error boxes around a given sky position. Sources from the UTR-2 catalogue (Braude et al. 1978--1994), observed at decametric wavelengths (10--25 MHz) with an antenna beam of about 40$'$, were cross-identified with entries from other radio catalogues at higher frequencies. Using the CATS database we extracted all sources within 40$'$ around UTR positions to find candidate identifications. A spectrum for each source was fitted with a set of curves using a least-squares method to find the best fit. We preferentially selected radio counterparts whose radio spectrum extrapolated to low frequencies matched the UTR decametric flux densities, and whose coordinates were close to the gravity center of UTR positions. Among all the 1822 sources in the UTR catalogue we found about 350 sources to be blends of two or more sources. As the most probable true coordinates of the radio counterparts we used positions from the NVSS, TXS, GB6, or PMN catalogues. Using low-frequency sources (26, 38, 85 MHz) from CATS we checked the reliability of some of our IDs. We show examples of the above methods, including raw and ``cleaned'' spectra.

astro-ph↗
arXiv1999

Low frequency catalogues of the CATS database

The authors describe the largest existing publicly accessible radio source database CATS (``astrophysical CATalogues Supporting system''; http://cats.sao.ru). CATS contains more than 300 catalogues of objects detected in different (but mostly radio) wavelength ranges. These include catalogues from the largest existing surveys, like NVSS, FIRST, WENSS, TXS, GB6, IRAS, ROSAT, PGC, MCG, etc. Thus CATS allows to draw samples of objects to study a great variety of astrophysical problems. CATS also includes all of the largest low-frequency catalogues published so far : UTR(10--25 MHz), Culgoora (80, 160 MHz), Cambridge (38, 151, 178 MHz), Miyun (232 MHz), WENSS (325 MHz), Texas (365 MHz), Bologna and Molonglo (408 MHz) etc., and allows the user to operate with them.

astro-ph↗
arXiv1999

5 radio sources of the Zenith survey at RATAN-600: VLA maps, radio spectra and optical identification

VLA maps obtained at 1.4 GHz with a resolution of 2\farcs5$\times$2\arcsec for three sources and 6\farcs5$\times$2\farcs3 for two sources detected in the RATAN-600 Zenith survey of 1988 have been analyzed. All five objects have an extended structure. Continuous radio spectra of these objects prepared by using the CATS database and RATAN-600 observations are given. All five objects have linear steep spectra ($α< -0.65$). Using APM database and DSS we have found three candidates for identification. Two radio sources have been observed with the 6 m telescope. The nature of the studied objects, one of which is classified as QSO (BSO) and two others as galaxies, is discussed. One of the radio sources, RZ5, being a merging group of one large and several small galaxies, may have appeared in this process.

astro-ph↗
arXiv1999

Radio emission of Shakhbazian Compact Galaxy Groups

Three hundred fifty three radio sources from the NRAO VLA Sky Survey (NVSS) (Condon et al. 1998) and the FIRST Survey (White et al. 1997}, are detected in the areas of 179 Shakhbazian Compact Groups (ShCGs) of galaxies. Ninety three of them are identified with galaxies in 74 ShCGs. Six radio sources have complex structure. The radio spectra of 22 sources are determined. Radio luminosities of galaxies in ShCGs are in general higher than that of galaxies in Hickson Compact Groups (HCGs). The comparison of radio (at 1.4 GHz) and FIR (at 60 $μ$m) fluxes of ShCG galaxies with that of HCG galaxies shows that galaxies in ShCGs are relatively stronger emitters at radio wavelengths, while galaxies in HCGs have relatively stronger FIR emission. The reasons of such difference is discussed.

astro-ph↗
arXiv1996

Preparing a public database of radio sources

We have collected the largest existing set of radio source lists in machine-readable form: 320 tables with 1.75 million records. Only a minor fraction of these is accessible via public databases. We describe our plans to make this huge amount of heterogeneous data accessible in a homogeneous way via the World Wide Web, with reliable cross-identifications, and searchable by various observables.

astro-ph↗