HI Absorption in GPS/CSS Sources

Abstract

Combining our own observations with data from the literature, we consider the incidence of HI absorption in gigahertz peaked spectrum (GPS) and compact steep spectrum (CSS) sources. Here we present our preliminary results, where we find that the smaller GPS sources (<1 kpc) on average have larger HI column densities than the larger CSS sources (>1 kpc). Both a spherical and an axi-symmetric gas distribution, with a radial power law density profile, can be used to explain this anti-correlation between projected linear size and HI column density. Since most detections occur in galaxy classified objects, we argue that if the unified schemes apply to the GPS/CSS sources, a disk distribution for the HI is more likely.