http://arxiv.org/abs/1808.05115
We analyze differences in positions of active galactic nuclei between Gaia data release 2 and VLBI and compare the significant VLBI-to-Gaia offsets in more than 1000 objects with their jet directions. At least 3/4 of the significant offsets are confirmed to occur downstream or upstream the jet representing a genuine astrophysical effect. By introducing redshift and Gaia color into analysis, we are able to distinguish between the effect of the host galaxy, jet, and accretion disk. Strong optical jets being at least 20-50-pc long are required to explain the offsets downstream. Offsets upstream of up to 2 mas are at least partly due to the dominant impact of the accretion disk on the Gaia coordinates and by the effects of parsec-scale radio jet. The host galaxy was found not to play an important role in the detected offsets. BL Lacertae object, radio galaxies, and Seyfert 2 galaxies are observationally confirmed to have a relatively weak disk and consequently downstream offsets. The disk dominates in the Gaia band and drives upstream offsets in a significant fraction of quasars and Seyfert 1 galaxies depending on the relative brightness of the disk and jet. The observed behaviour of the different AGN classes is consistent with the unified scheme assuming varying contribution of the obscuring dusty torus and jet beaming.
A. Plavin, Y. Kovalev and L. Petrov
Thu, 16 Aug 18
8/46
Comments: 5 pages, 5 figures; Submitted to ApJL