Deep 8.4 GHz VLBI Images of Seven Faint Nuclei in Lobe‐dominated Quasars

Abstract

We present deep 8.4 GHz VLBI images of the faint nuclei in seven lobe-dominated quasars (LDQs): 3C 175, 3C 204, 3C 205, 3C 215, 3C 351, 0821)447, and 0839)616 . These images, made from data obtained in 1988 and 1991 with high-sensitivity VLBI arrays, have a typical rms noise level of D0.03 mJy per beam and resolution of D0.5 mas. The parsec-scale jet structures are generally greater in extent and complexity than those seen on many previous, less sensitive maps of other LDQ nuclei; the jet in 3C 204 bends through at least 10i, and the jet in 3C 205 extends out to D5 mas. Observations of 3C 204, 3C 205, and 0839)616 at two epochs reveal clear —ux density variability in 3C 204 and 3C 205, but none of these sources shows any evidence for outward motion of jet components; their mean appar- ent transverse velocity is ((0.47 ^ 0.43)h~1c, from which we determine a 3 p upper limit on their mean expansion speed of D0.8 h~1c km s~1 Mpc~1, The innermost jet knot in 3C 204 (H 0 100 hq 0 0.5). underwent a marginal position angle swing away from the mean jet axis. We also present the —rst 8.4 GHz A-array VLA images for all the objects except 3C 351. All the sources except 0821)447 display one-sided VLBI and VLA jets, which lie on the same side of the VLBI core and are generally well aligned (to within D5i). In addition, we analyze the statistics of projected linear size, relative nuclear strength, and misalignment angle for the 3CR and Jodrell Bank LDQ samples. We conclude that our results are generally consistent with a fairly simple relativistic jet model and with the uni—cation of core- dominated quasars, lobe-dominated quasars, and possibly even powerful radio galaxies; there is a mar- ginal suggestion that the quasars in our samples have a restricted range of angles to the line of sight (e.g., 0i to D45i). Subject headings: galaxies: jetsgalaxies: structurequasars: generalradio continuum: galaxies ¨ techniques: interferometric