Spitzer Space Telescope - Directors Discretionary Time Proposal #496


IRS Observations of a Strongly Lensed LIRG Behind the Bullet Cluster

Principal Investigator: Anthony Gonzalez
           Institution: University of Florida

     Technical Contact: Anthony Gonzalez, University of Florida

Co-Investigators: 
Marusa Bradac, UCSB
Doug Clowe, Ohio University
Christine Jones, Harvard-Smithsonian Center for Astrophysics
Maxim  Markevitch, Harvard-Smithsonian Center for Astrophysics
Greg Rudnick, NOAO
Casey Papovich, Texas A&M
Dennis  Zaritsky, University of Arizona

Science Category: high-z galaxies
 Observing Modes: IrsMap IrsPeakUpImaging
  Hours Approved: 6.0

Abstract:
We propose to observe a luminous infrared galaxy at z~2.7 that is highly 
lensed (factor of ~50 magnification) by the Bullet Cluster. This galaxy is 
a strong 24 micron and submillimeter source due to this magnification, yet 
the intrinsic infrared luminosity of this galaxy is lower than any other 
obscured galaxies previously observed with IRS at these redshifts. We will 
use IRS spectra and peak-up imaging to (1) obtain a spectroscopic redshift, 
(2) quantify the AGN contribution to the observed 24 micron emission, and 
(3) determine the star-formation rate from the Paschen alpha line. IRS is 
required because there is no other means of achieving these objectives; 
DDT is required because the 24 micron data on which this program is based 
was obtained after the Cycle 5 deadline.