Spitzer Space Telescope - Archive Research Proposal #50100


The Dust - AGN Connection in Early-Type Galaxies

Principal Investigator: Paul Martini
           Institution: Ohio State University

     Technical Contact: Paul Martini, Ohio State University

Co-Investigators: 
Thaisa Storchi-Bergmann, UFRGS                                        
Ramiro Simoes Lopes, UFRGS                                            

Science Category: nearby galaxies (z<0.05, v_sys<15,000 km/s) 
Dollars Approved: 100000 

Abstract:
While many efforts over the years have searched for evidence of the fueling
mechanism(s) of Active Galactic Nuclei, we recently identified the first
substantial difference between the hosts of AGN and inactive galaxies: all AGN
in early-type galaxies show evidence for circumnuclear dust, while dust is only
present in a minority (about 25%) of inactive, early-type galaxies. These
observations suggest that circumnuclear dust, within hundreds of parsecs of the
centers of these galaxies, is a necessary condition for fueling the central,
supermassive black hole, and that the AGN may affect the observed dust
morphology or its absence. However, this analysis was based on HST observations
that were primarily sensitive to clumpy dust on small scales, rather than the
diffusely distributed dust identified in many infrared studies of elliptical
galaxies. As over 90% of our sample (60 galaxies) have archival Spitzer IRAC and
MIPS observations, we propose to search for diffuse dust between our
well-matched sample of AGN and inactive galaxies and determine if these
pronounced differences also hold for diffuse dust. We will also use these
infrared observations to estimate the total attentuation by dust and place
constraints on the total dust mass in ellipticals, which can be used to infer
the dust survival time against sputtering.