VLBI at the highest frequencies - AGN studied with micro-Arcsecond resolution

Abstract

Compact galactic and extragalactic radio sources can be imaged with an unsurpassed angular resolution of a few ten micro-Arcseconds, adopting the observing technique of global millimeter VLBI. Here, we present the Global Millimeter VLBI Array (GMVA) and discuss its present performance. We show and discuss new results obtained with the GMVA for individual and partially archetypal radio sources with prominent VLBI jets (e.g. 3C 120, CygnusA,M87, 3C 454.3, NRAO150). The variety of observed effects range from jet propagation and bending, partial foreground absorption in the nucleus, and jet component ejection after major flares to new and very small (15-20 Schwarzschild radii) upper limits to the jet base of M87. We also discuss the future development of mm-VLBI at 3mm and towards shorter wavelengths, and make suggestions for possible improvements.