MILLIARCSECOND STRUCTURES OF EXTREMELY DISTANT QUASARS - 0336-017, 0636+680, 1442+101, AND 2048+312

We present the results of a continuing study of the milliarcsecond str ucture of extremely high-redshift radio sources aimed at investigating possible cosmological evolutionary effects in quasars and their use i n testing cosmological models. We present VLBI maps of four quasars at redshifts z greater than or equal to 3: 0336-017 (z = 3.197), 0636+68 0 (z = 3.174), 1442+101 (z = 3.531), and 2048+312 (z = 3.185). All fou r sources are resolved. Two, 0636+680 and 1442+101, show well defined jets, while the other two are slightly extended and may contain jets. A means of estimating the cosmological deceleration parameter q(o), us ing these and earlier data (Gurvits et al. 1992) is shown.