Spitzer Space Telescope - Guaranteed Time Observer Proposal #30318


Life Cycle of Dust in Elliptical Galaxies

Principal Investigator: Giovanni Fazio
           Institution: Harvard-Smithsonian Astrophysical Observatory

Co-Investigators: 
Michael Pahre, SAO                                                    
Tod Lauer, NOAO                                                       
Sandra Faber, UCSC                                                    
Christine Jones, SAO                                                  
William Forman, SAO                                                   

Science Category: nearby galaxies (z<0.05, v_sys<15,000 km/s) 
 Observing Modes: IracMap MipsPhot 
  Hours Approved: 32.0 

Abstract:
The old concept of ISM-free elliptical galaxies was discarded when
roughly half of early-type galaxies were detected at 60  um by IRAS.
Nonetheless, little is known to date on the nature of the warm ISM in
this class of galaxies, since "normal" elliptical galaxies were not
often observed in space missions since IRAS.  Questions such as:
Where is the dust?  How does its temperature vary within a galaxy and
among galaxies?  How is the presence of dust related to AGN activity?
And, especially, what are the probable origins, reservoirs, and life
cycles of the dust in elliptical galaxies?  Early Spitzer observations
have found tantalizing examples where the dust is organized into
features (arms, rings, disks) reminiscent of disks of spiral galaxies,
which could have profound implications for understanding the origin of
the Hubble morphological sequence.  We propose to obtain moderately
deep imaging with Spitzer from 3.6 to 160um of a sample of galaxies
that is well studied optically (with HST imaging) in order to address
these questions.  The outcome of the project will be a broad picture
of the origin and fate of the dust and its properties (mass,
temperature, size distribution, PAH content) as a function of location
within the galaxies.  These data will also make a large and lasting
contribution to the legacy of archival data from the Great
Observatories on the global properties of nearby, normal galaxies.