DJp.2.16 — HST images of FeLoBAL quasars: Testing quasar-galaxy evolution models

Date & Time

Aug 10th at 6:00 PM until 6:00 PM




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Author(s): Hanna Herbst3, Fred Hamann3, Paola Caselli1, Anton M. Koekemoer2, Carolin Villforth5, Sylvain Veilleux4

Institution(s): 1. Max Planck Institute for Extraterrestrial Physics, 2. Space Telescope Science Institute, 3. University of Florida, 4. University of Maryland, 5. University of St Andrews

We present preliminary results from an HST imaging study of FeLoBAL quasars, which have extremely low-ionization Broad Absorption Line (BAL) outflows and might be a young quasar population based on their red colors, large far-IR luminosities (suggesting high star formation rates), and powerful outflows. Some models of quasar - host galaxy evolution propose a triggering event, such as a merger, to fuel both a burst of star formation and the quasar/AGN activity. These models suggest young quasars are initially obscured inside the dusty starburst until a "blowout" phase, driven by the starburst or quasar outflows like FeLoBALs, ends the star formation and reveals the visibly luminous quasar. Despite the popularity of this evolution scheme, there is little observational evidence to support the role of mergers in triggering AGN or the youth of dust-reddened quasars (such as FeLoBALs) compared to normal blue quasars.

Our ongoing HST program is designed to test the youth of FeLoBAL quasars and the connection of FeLoBALs to mergers. We obtain WFC3/IR F160W images of 10 FeLoBAL quasars at redshift z~0.9 (covering ~8500A in the quasar rest frame). We compare the host galaxy morphologies and merger signatures of FeLoBALs with normal blue quasars (which are older according to the evolution model) and non-AGN galaxies matched in redshift and stellar mass. If FeLoBAL quasars are indeed in a young evolutionary state, close in time to the initial merging event, they should have stronger merger features compared to blue quasars and non-AGN galaxies. Preliminary results suggest that this is not the case - FeLoBAL quasars appear to reside in faint, compact hosts with weak merger signatures. We discuss the implications of these results for galaxy evolution models and other studies of dust-reddened quasar populations.