Circumnuclear HI Disk in the Compact Symmetric Object 4C31.04

摘要

Compact Symmetric Objects (CSO's) are strong, compact (<1kpc) objects with radiostructure and luminosity similar to classical double radio sources (i.e. two lobes and a weak core), but thousands of times smaller. It has been proposed that CSO's are either young radio sources which will later evolve into classical sources, or sources whose growth is 'frustrated' by dense surrounding gas. In a recent survey of z < 0.1 CSO's searching for HI absorption, approximately 50% were detected, a much higher percentage than found in surveys of general radio loud ellipticals with similar sensitivity.