APPARENT MILLIARCSECOND SIZES OF ACTIVE GALACTIC NUCLEI AND THE GEOMETRY OF THE UNIVERSE

The behavior of the characteristic angular size (as defined in the pap er) of milliarcsecond structures of active galactic nuclei (AGN) is an alyzed as a function of redshift (z). Such a dependence contains a wel l-known feature, a dependence of the apparent angular size of a standa rd rod on cosmological distance. However, in the discussed case, this general dependence is complicated by dependences of source linear size (l) on its luminosity (L) and redshift, l proportional to L(beta) (1 + z)(n). A nonlinear regression model, containing as parameters charac teristic linear size of AGN, indices beta and n, and the cosmological deceleration parameter q(0) was applied for observational data of the VLBI survey at 2.3 GHz (Preston et al. 1985). Results of the regressio n models are discussed from the perspective of apparent and intrinsic properties of milliarcsecond structures of AGN. The best fit is obtain ed for parameters beta = 0.26 +/- 0.03 and n = -0.30 +/- 0.90. In the particular case of the universe with the Robertson-Walker metric and z ero cosmological constant, the estimated value q(0) = 0.16 +/- 0.71 is somewhat favorable for the open cosmological models.