Hubble Space Telescope NICMOS observations of the host galaxies of powerful radio sources: Does size matter?

We present near-infrared J- and K-band imaging of a sample of powerful radi o source host galaxies with the Hubble Space Telescope NICMOS2 camera. Thes e sources have been selected on their double-lobed radio structure and incl ude a wide range of projected radio source sizes. The largest projected lin ear sizes range from the compact gigahertz peaked spectrum (GPS; <1 kpc) an d compact steep spectrum (CSS; <20 kpc) radio sources, up to the large-scal e (>20 kpc) classical doubles (FR II radio sources). We investigate the dep endence of host galaxy properties (including near-IR surface brightness pro files) on radio source size, using both our own and published data. The abs olute magnitudes and surface brightness profiles are consistent with the ho st galaxies being regular giant elliptical galaxies rather than brightest c luster galaxies (BCGs). We find that the GPS, CSS, and FR II host galaxies are a uniform class of objects, consistent with a scenario in which a power ful radio source evolves along this size sequence.