3C 48: Stellar Populations and the Kinematics of Stars and Gas in the Host Galaxy

We present deep Keck LRIS spectroscopy of the host galaxy of 3C 48. Ourobservations at various slit positions sample the different luminous componentsnear the quasar, including the apparent tidal tail to the NW and several strongemission line regions. By fitting Bruzual & Charlot (1996) population synthesis models to ourspectra, we obtain ages for the most recent major episodes of star formation invarious parts of the host galaxy covered by our slits. There is vigorouscurrent star formation in regions just NE and SE of the quasar andpost-starburst regions with ages up to ~10^8 years in other parts of the hostgalaxy, but most of the NW tidal tail shows no sign of significant recent starformation. We use these model fits, together with the kinematics of the starsand gas, to outline a plausible evolutionary history for the host galaxy, itsrecent starburst activity, the triggering of the quasar, and the interaction ofthe radio jet with the ambient gas. There is strong evidence that the 3C 48 host is an ongoing merger, and thatit is probably near the peak of its starburst activity. Nevertheless, thequasar itself seems to suffer little extinction, perhaps because we are viewingit along a particularly favorable line-of-sight.