Back to Volume
Paper: Compact Structures in Flat-Sprectrum Extragalactic Radio Sources
Volume: 300, Radio Astronomy at the Fringe
Page: 65
Authors: Kovalev, Y.Y.
Abstract: We have used visibility data obtained with the VLBA at 15 GHz to examine the most compact structures in 160 flat-spectrum extragalactic radio sources. With projected baselines out to 440 million wavelengths we are able to study source structure on angular scales as small as 0.12 mas. For about 40% of the sources, at least at one epoch, more than half of the flux density is unresolved on the longest baselines. These objects may have dimensions less than 0.12 mas. The most variable sources tend to have the most compact structure. Typical lower limits to the brightness temperature are in the range of 1011 to 1012 K but extend up to 1013 K; this being an apparent excess of the inverse Compton limit for stationary synchrotron sources. Longer baselines, such as shall be available in future space VLBI missions, are needed to study the most compact high brightness temperature regions in these sources. The fringe visibilities of the γ-ray loud AGN show, on average, higher values than for γ-ray quiet AGN and they are more variable. This supports a concept of a common emission mechanism at radio and γ-ray wavelengths. A visible correlation of VLBI-filled aperture monitoring data is also discussed.
Back to Volume