Space VLBI and the physics of active galactic nuclei

Abstract

Three related questions are considered: 1) The number of sources observable with the highest resolution of Radioastron and VSOP. 2) The ability of space VLBI to map structures in the AGN cores. 3) The use of space VLBI for testing orientation-dependent unified models of AGN. At 22 GHz Radioastron may be able to observe only a handful of sources at any given time due to the required high minimum brightness temperature, and the most useful observing strategy may be to observe repeatedly a few sources to map the geometry and the evolution of jet and shock structures. For survey-type observing programs VSOP is more suitable. By measuring apparent transverse velocities in BL Lacs and other very compact sources with space VLBI and deducing the Doppler boosting factors from continuum monitoring, orientation angles can be determined and the relationship between different classes of AGN established.