STScI Preprint #1226

Hosts of Powerful Radio Galaxies in the Near-IR: Implications for Radio Source Evolution

Using KPNO 2.1m J, H, and K-band data on samples of Gigahertz Peaked Spectrum (GPS, radio size <1kpc), Compact Steep Spectrum (CCS, 1-20kpc), and 3CR classical doubles (>20kpc), we have constructed mean broadband spectral energy distributions (SEDs) for each of the object classes and compared these with synthetic SEDs. The host galaxies of the compact and extended radio sources appear to have similar near-IR broadband SEDs, implying similar stellar populations and AGN. These SEDs are best fit with a mean metallicity of ~solar and fairly old stellar populations implying formation redshifts of 5. Redshift evolution of the sources is consistent with a passive evolutionary model. In addition, an extra IR component is needed which can be modelled by emission from dust at a temperature of 900-1300 K, perhaps produced by the putative obscuring torus. All of our results are consistent with the hypothesis that the GPS and CSS are the progenitors of the large scale 3CR radio galaxies.

Status:

Appeared in: The Astrophysical Journal, 503:156-167, 1998

Affiliations:

¹)Space Telescope Science Institute, 3700 San Martin Drive Baltimore, MD 21218, USA
²)also at Kapteyn Astronomical Institute
³)Leiden Observatory, P.O. Box 9513, NL-2300 RA, Leiden, The Netherlands
⁴)Kapteyn Astronomical Institute, P.O. Box 800, NL-9700 AV, Groningen, The Netherlands