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The SEDs database "Evolution of radio galaxies"


Following people are working to realiaze this project:
Oleg V. Verkhodanov vo@sao.ru
Alexander I. Kopylov akop@sao.ru
Olga P. Zhelenkova
Natalia V. Verkhodanova nat@sao.ru
Vladimir N. Chernenkov

This work is carried out in collaboration with

Yu.N.Parijskij par@sao.ru
N.S.Soboleva sns@fsao.spb.su
A.V.Temirova tem@fsao.spb.su


The last few years have changed our view on the evolution of galaxies: the most distant galaxies (i.e. systems having stellar population) have been found at redshift z=6.68 (Chen H.-W., Lanzetta, K. M., Pascarelle, S. 1999, Nature, 398, 586) and radio galaxy at z=5.19 (van Breugel W., De Breuck C., Stanford S. A., Stern D., Rottgering H., Miley G. 1999. astro-ph/9904272 ). Some of models suggests that galaxies can start their formation at z=17 (Chen H.-W., Lanzetta, K. M., Pascarelle, S. 1999. astro-ph/9907002 ).

To understand deeper a situation with a stellar population of galaxies and to check various mordern models it is very important to have a capability to detect correctly an age of galaxies.

The labour intensity of obtaining statistically significant high-quality data on distant and faint galaxies and radio galaxies forces one to look for simple indirect procedures in the determination of redshifts and other characteristics of these objects. With regard to radio galaxies, even photometric estimates turned out to be helpful and have so far been used (McCarthy P.J. 1993. An. Review. Astron. Astroph., 31, 639; Benn C.R., Wall J., Vigotti M., Grueff G., 1989. MNRAS, 235, 46).

In the late 1980s and early 1990s it was shown that the color characteristics of galaxies can yield also the estimates of redshifts and ages for the stellar systems of the host galaxies. Numerous evolutionary models appeared with which observational data were compared to yield results strongly differed from one another (Arimoto N., Yoshii Y. 1987. Astron. Astroph., 179, 23; Chambers K., Charlot S., 1990. Astrophys. J. Lett., 348, L1; Lilly S. MNRAS, 1987, 229, 573; Lilly S. 1990. In "Evolution of the Universe", ed. Kron R.G., Astron. Soc. Pacific, 344).

Over the last few years the three models: PEGASE (Project de'Etude des Galaxies par Synthese Evolutive (Fioc M., Rocca-Volmerange~B. Astron. Astroph., 1997, 326, 950)), Poggianti B.M. (1997. Astron. Astroph., 122, 399) and GISSEL'96 (Bruzual, Charlot, 1996), have been extensively used, in which an attempt has been made to eliminate the shortcomings of the previous versions.

In the "Big Trio" experiment (Parijskij Yu. N., Goss W.M., Kopylov A.I., Soboleva N.S., Temirova A.V., Verkhodanov O.V., Zhelenkova O.P., Naugolnaya M.N. 1996. Bulletin SAO, 40, 5) we also attempted to apply these techniques to distant objects of the RC catalogue with ultra steep spectra (USS). Color data for nearly the whole basic sample of USS FRII (Fanaroff B.L., Riley J.M. 1974, MNRAS, 167, 31). RC objects have been obtained with the 6m telescope of SAO RAS.

To accelerate a procedure of age (and photometric redshift) estimation we have begun a project "Evolution of radio galaxies", supported by the Russian Foundation of Basic Research (grant 99-07-90334), which has to allow a user to obtain age and photometric redshift estimations.

Description of a system

This system, being developed at present, will allow a user to operate with simulated curves of spectral energy distributions (SED) to estimate ages and redshifts by photometral data. Authors use SEDs of three models: for different types of galaxies.

The system will be situated on the special Web-server unifying various type resources, including specialized Internet protocol daemons (for the FTP, HTTP, e-mail support) and the designed software permitting a user to operate with the SED curves.

Requesting and filling in the standard HTML-forms a user will be able to select different types of curves or trust to do this to a computer by the \Chi^2 method. The input forms contain information about input filters or wavelengths and corresponding magnitudes.

There will be a possibility to detect the age of galaxies in two ways:

  1. fixed (known) redshift;
  2. variable (unknown) redshift. In this case the redshift will be estimated too.

The estimation of ages and redshifts is performed by way of selection of the optimum location on the SED curves of the measured photometric points obtained when observing radio galaxies in different filters. We use the already computed table SED curves for different ages. The algorithm of selection of the optimum location of points on the curve consists briefly (for details see Verkhodanov O.V., 1996, Bulletin SAO, 41, 149) in the following: by shifting the points lengthwise and transverse the SED curve such a location is to be found at which the sum of the squares of the discrepancies is a minimum. Through moving over wavelengths and flux density along the SED curve we estimate the displacements of the points from the location of the given filter and then the best fitted positions are used to compute the redshift. From the whole collection of curves, we select the ones on which the sum of the squares of the discrepancies turn out to be minimal for the given observations of radio galaxies.

There will be a chance to use infrared maps for absorption estimates in a case when magnitudes are not corrected for absorption.

In order to take account of the absorption, we apply the maps (as FITS-files) from the paper "Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds" (Schlegel D., Finkbeiner D., Davis M. 1998. Astrophys. J. 500, 525).

The conversion of stellar magnitudes to flux densities are performed by the standard formula: S(Jy)=10^(C-0.4m).

Another possibilities are supposed to be supported in our system:

The HTTP and e-mail access to the basic procedures is organized in this system. Special e-mail forms are prepared to reflect input flags of low level procedures.

FTP access is organized to give a user a possibility to obtain SEDs models recorded in separate files.

A result is supposed to be written in ASCII tables and PS-figures and can be sent to users.

An example of request execution, recorded in PS-files, is shown in Figures. (see detailed description and application of this approach also in Verkhodanov O.V., Kopylov A.I., Parijskij Yu.N., Soboleva N.S., Temirova A.V. 1999. Bulletin SAO, 48, 41. astro-ph/9910559):

optimum SED and position of photometry points Probality function Estimation of age and redshift for the 4C+24.28 radio galaxy in the PEGASE model are shown in these figures. SED curves with photometric data marked with crosses are shwon on the left panels. Contours of likelihood functions vs redshift and log age are plotted at levels 0.6, 0.7, 0.9. 0.97 on the right panels.


Verkhodanov O.V.. 1996, On one algorithm of fitting of the function, preassigned by table, to tabular defined points. Bulletin SAO, 41, 149.

Verkhodanov O.V., Kopylov A.I., Parijskij Yu.N., Soboleva N.S., Temirova A.V. 1999. Redshifts and age of stellar systems of distant radio galaxies from multicolour photometry data. Bulletin SAO, 48, 41. astro-ph/9910559.

Verkhodanov O.V.. Radio galaxies. Lecture in Russian (koi-8).

O.V.Verkhodanov, A.I.Kopylov, O.P.Zhelenkova, N.V.Verkhodanova, V.N.Chernenkov, Yu.N.Parijskij, N.S.Soboleva, A.V.Temirova. 2000. The software system ``Evolution of radio galaxies''. Atsron. Astrophys. Trans. V.19, No 3-4, PP. 662-667. astro-ph/9912359.

Verkhodanov O.V., Kopylov A.I., Zhelenkova O.P., Verkhodanova N.V., Chernenkov V.N., Parijskij Yu.N., Soboleva N.S., Temirova A.V. 1999. The SEDs database "Evolution of radio galaxies". In Book of Abstracts "The Universe at Low Radio Frequencies", IAU Symp.199, Nov.30-Dec.4, P.23, No.A P-1.

O.V.Verkhodanov, A.I.Kopylov, O.P.Zhelenkova, N.V.Verkhodanova, V.N. Chernenkov. 2000. The informational system "Evolution of radio galaxies". In Proc. of the International Workshop on Computer Science and Information Technologies. CSIT'2000. Ufa, Russia, September 18-23, 2000. V.2, pp. 235-239

Yu.N. Parijskij, W.M. Goss, A.I. Kopylov, N.S. Soboleva, A.V. Temirova, O.V. Verkhodanov, O.P. Zhelenkova. 2000. RATAN-600 - VLA - BTA-6m ("Big Trio") project: multicolour studying of distant radio galaxies. Atsron. Astrophys. Trans. V.19, No 3-4, PP.297-304, astro-ph/0005240.

Verkhodanov O.V., Kopylov A.I., Verkhodanova N.V., Zhelenkova O.P., Chernenkov V.N., Parijskij Yu.N., Soboleva N.S., Temirova A.V. Organization of the data base of spectral energy distributions of radio galaxies. In Book of Abstracts. Joint European and National Astronomical Meeting, JENAM'2000. 9th European and 5th Euro-Asian Astronomical Conference, held in Moscow, Russia, May 29 - June 3, 2000, P.181.

Yu.N.Pariiskii, N.S.Soboleva, A.I.Kopylov, O.V.Verkhodanov, A.V.Temirova, O.P.Zhelenkova, J.Winn, A.Fletcher, B.Burke. 2000. The Radio Galaxy RC J1148+0455. Astronomy Letters. V.26, No 7, P.423-427 (In Russian: Pis'ma v Astronomicheskij Zhurnal, V.26, No 7, P.493-498).

N.S.Soboleva, W.M.Goss, O.V.Verkhodanov, O.P.Zhelenkova, A.V.Temirova, A.I.Kopylov3, and Yu.N.Pariskii. 2000. RC J0105+0501: A Radio Galaxy with Redshift z=~3.5 Astronomy Letters. V.26, No 10, P.623-627. (In Russian: Pis'ma v Astronomicheskij Zhurnal, V.26, No 7, P.723-728).