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Astron. Astrophys. 342, 378-388 (1999)

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The "angular size - redshift" relation for compact radio structures in quasars and radio galaxies *

L.I. Gurvits 1,2, K.I. Kellermann 3 and S. Frey 1,4

1 Joint Institute for VLBI in Europe, P.O. Box 2, 7991 PD Dwingeloo, The Netherlands
2 Astro Space Center, P.N.Lebedev Physical Institute, 117924 Moscow, Russia
3 National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, Virginia 22903-2475, USA
4 FÖMI Satellite Geodetic Observatory, P.O. Box 546, H-1373 Budapest, Hungary

Received 24 June 1998 / Accepted 28 September 1998


We discuss the "angular size - redshift" relation for compact radio sources distributed over a wide range of redshifts [FORMULA]. Our study is based on a sample of 330 5 GHz VLBI contour maps taken from the literature. Unlike extended source samples, the "angular size - redshift" relation for compact radio sources appears consistent with the predictions of standard Friedmann world models with [FORMULA] without the need to consider evolutionary or selection effects due to a "linear size - luminosity" dependence. By confining our analysis to sources having a spectral index, [FORMULA], and a total radio luminosity, [FORMULA] W/Hz ([FORMULA] km s-1 Mpc- 1, [FORMULA] used as a numerical example), we are able to restrict the dispersion in the "angular size - redshift" relation. The best fitting regression analysis in the framework of the Friedmann-Robertson-Walker model gives the value of the deceleration parameter [FORMULA] if there are no evolutionary or selection effects due to a "linear size - luminosity", "linear size - redshift" or "linear size - spectral index" dependence.

Key words: galaxies: active – galaxies: quasars: general – cosmology: observations – radio continuum: galaxies

* Full version of Table 1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr ( or via http://cdsweb.u-strasbg.fr/Abstract.html

Send offprint requests to: L.I. Gurvits, 1st address (lgurvits@jive.nfra.nl)

© European Southern Observatory (ESO) 1999

Online publication: February 22, 1999