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Radio sources identfification

LABORATORY OF RADIO ASTRONOMICAL OBSERVATIONS

Radio sources identfification

Radio sources identification is one of the most important tasks of the current radio astrophysics. Just after identifcation of a source one can discuss its nature. Therefore, practically all groups of radio astronomers stdudying extragalactic and galactic objects meet the problem of identification. One can underline several directions of this activity:

Optical idetification.
Optical identification is carried out to determine the accurate coordinates of a parent objects of the radio source and its morphology. Identifcation can be done using Palomar Sky Survey (e.g. see an electronic version: http://stdatu.stsci.edu/dss/dss_form.html), digital analyzed plates ( http://www.ast.cam.ac.uk/~apmcat/ ), and, the most important, with observations at optical telescopes. Besides, if the object has been investigated in optics, it is possible to find it in published lists, which are particularly stored in the data base CATS.
To identify an object in optical images one has to determine astrometry coordinates of surrounding objects, find an optical candidate and estimate of probability of radio source identification, calculating likelihood function taking into account the density of objects in the optical frame. Using accurate optical coordinates one can investigate its spectroscopic properties.
One can find references and description of the optical identification in the following papers:

Kopylov A.I., Goss W.M., Parijskij Yu.N., Soboleva N.S., Temirova A.V., Zhelenkova O.P., Vitkovskij Val.V., Naugolnaya M.N., Verkhodanov O.V. 1995. Optical identifications of subsample of steep spectra radio sources from RC catalog using 6m SAO telescope of SAO RAS: optical observations. Astronomicheskij Zhurnal (Russia). V.72. No.5. P.613-629.
Verkhodanov O.V. Study of the objects of Zenith sky survey 1988. Astronomy Reports. V.38. P.307-313. (in Russian: Astronomicheskij Zhurnal. V. 71. No 3. P.352-359). 1994.
Parijskij Yu. N., Goss W.M., Kopylov A.I., Soboleva N.S., Temirova A.V., Verkhodanov O.V., Zhelenkova O.P., Naugolnaya M.N. Investigation of RATAN-600 RC radio sources. Bulletin of SAO, No 40, 1996, P. 5-124.

Verkhodanov O.V., Verkhodanova N.V. 1999. Study of some sources near the sky region of 47 degrees by declination at RATAN-600. Astronomicheskij Zhurnal. In press.
Radio identification.
Identification of radio sources with data of various radio catalogs allows one to construct continual spectrum of the object and its radio structure. Spectrum is a function of flux density vs frequency. To construct spectrum one can take into account calibration factor to operate in the unified flux density scale (e.g., the most frequently used scale is the Baars's scale) and date of observation, because a radio source may be variable. Besides the list of radio sources, the result of current radio surveys is the sky radio brightness distribution, which is used to determine a structure of the object. One can study a radio structure using radio surveys NVSS, FIRST, WENSS. Practically all the largest radio catalogs can be found in the CATS database.
One can find references and description of the radio identification and study of continual radio spectra in the following papers:

Bursov N.N., Chepurnov A.V., Lipovka N.M., Soboleva N.S., Temirova A.V. 1993. The spectral characteristics of the RATAN-600 RC-catalog sources. Astron. Astrophys. Suppl. Ser. V.101. P.447

Bursov N.N. 1996 Spectra of radio sources of the program "Cold" at the RATAN-600 radiotelescope. Bull. SAO. V.40. P.128.

Trushkin S.A. 1996. Multi-frequency observations of supernova remnants with the RATAN-600 radio telescope. Bull. SAO. V.41. P.64

Trushkin S.A. 1998. The Ratan Galactic Plane Survey IAU Symp. V.179. P.103

Verkhodanov O.V. Study of the objects of Zenith sky survey 1988. Astronomy Reports. V.38. P.307-313. (in Russian: Astronomicheskij Zhurnal. V. 71. No 3. P.352-359). 1994.
Verkhodanov O.V., Verkhodanova N.V. 1999. Study of some sources near the sky region of 47 degrees by declination at RATAN-600. Astronomicheskij Zhurnal. In press.
Verkhodanov O.V., Andernach H., Verkhodanova N.V. 1997. Interactive restoration of radio spectra of UTR sources. In "Problems of modern radio astronomy" (in Russian). Proc. of the 27th Radio astronomical conf. St.-Petersburg. Institute of Applyment Astronomy of RAS. V.1. P.330-331.
Identifcation with X-ray sources.
The study of activity of the objects is carried out not only in radio wavelength range, but also in X-rays. There are several sky surveys carried out with X-ray telescopes situated on the near Earth orbit. The largest X-rays surveys are the surveys carried out with the ROSAT satellite. One can find information about these catalogs in the CATS database.
Catalogs cross-identification
Using the completeness one can investigate statistical properties of obects in the various wavelength ranges with cross-identification of these catalogs. Special functions have been designed in the CATS database permitting to cross-identify the catalogs. Several lists of objects obtaing with such operations are studied now.
Results of study have been particularly piblished in the following papers:

S.A.Trushkin, O.V.Verkhodanov, 1995, On the cross-identification of the IRAS-Point Source and Texas catalogs. Bulletin of SAO, No 39, P.150-154.

Verkhodanov O.V., Trushkin S.A. 1997. Cross-identification of the Texas catalog at 365 MHz and 3 main catalogs of the satellite IRAS. In "Problems of modern radio astronomy" (in Russian). Proc. of the 27th Radio astronomical conf. St.-Petersburg. Institute of Applyment Astronomy of RAS. V.1. P.332-333.
Trushkin S.A., Verkhodanov O.V. 1997. Spectra and statistical properties of ITA catalog objects. In "Problems of modern radio astronomy" (in Russian). Proc. of the 27th Radio astronomical conf. St.-Petersburg. Institute of Applyment Astronomy of RAS. V.1. P.328-329.
Verkhodanov O.V., Andernach H., Verkhodanova N.V. 1997. Interactive restoration of radio spectra of UTR sources. In "Problems of modern radio astronomy" (in Russian). Proc. of the 27th Radio astronomical conf. St.-Petersburg. Institute of Applyment Astronomy of RAS. V.1. P.330-331.
Verkhodanov O.V., Andernach H., Verkhodanova N.V.: 1998, "On the properties of decametric sources (by identifications in the CATS database)", in Proc. XV Conf. on "Aktualnye problemy vnegalakticheskoi astronomii" ("Current Problems of Extragalactic Astronomy"), Pushchino, May 25--29, 1998, printed in Pushchino Sci. Center, p.15-18 (in Russian).

vo@sao.ru

(Oleg Verkhodanov)