Spitzer Space Telescope - General Observer Proposal #20000


Gotcha!  Using Swift GRBs to Pinpoint the Highest Redshift Galaxies

Principal Investigator: Edo Berger
           Institution: Carnegie Observatories

Co-Investigators: 
Lennox Cowie, U. Hawaii                                               
Ranga-Ram Chary, Spitzer Science Center                               
Derek Fox, Caltech
Shirnivas Kulkarni, Caltech                                           
Paul Price, U. Hawaii                                                 
Joshua Rich, Australian National University
Patrick McCarthy, Carnegie Institution of Washington                  
Michael Rauch, Carnegie Institution of Washington                     
Alicia Soderberg, Caltech                                             
Bradley Cenko, Caltech                                                
Michael Gladders, Carnegie Institution of Washington                  
Kurt Adelberger, Carnegie Institution of Washington
Amy Barger, U. Wisconson, Madison
Brian Schmidt, Australian National University                         
Bruce Peterson, Australian National University                        
George Djorgovski, Caltech                                            

Science Category: GRBs 
 Observing Modes: IracMap 
  Hours Approved: 17.0 

Abstract:
While there is convincing evidence that the Universe was re-ionized
between redshifts of 6.5 and 15, the role of galaxies in this process
is still not understood.  Several star-forming galaxies at z~6 have
been identified in recent deep, narrow-field surveys, but the
expensive observations along with cosmic variance and contamination
make it difficult to assess their contribution to re-ionization.
Moreover, the detection of galaxies at z>7 is exceedingly difficult
even with the Hubble UDF or cluster lensing.  Significant progress can
be made using gamma-ray bursts (GRBs) localized with the
now-operational Swift satellite, which is capable of detecting bursts
out to z>10.  GRBs have the advantage of being an uncontaminated
signpost for star-formation, and their afterglows are sufficiently
bright even at z>6 to allow photometric selection (via the Ly-alpha
drop out technique) with 2-5 meter telescopes.  Using our approved TOO
programs at an extensive range of facilities (from 1-m robotic
telescopes to Keck/Magellan), we can rapidly find afterglows at z>6
and easily distinguish them from dusty low redshift bursts.  This
approach is highly efficient compared to current techniques,
especially at z>7.  Here we request imaging with NICMOS (z>6), ACS
(z~6), and Spitzer/IRAC to characterize the properties (SFR, age,
morphology) of up to five galaxies located in this manner, and begin
to address their role in re-ionization.  These observations are
requested as >2 month TOOs, allowing flexibility of scheduling and at
the same time taking a unique and timely advantage of the exquisite
performance of three of NASA's premier missions.

This is an HST Cycle 14 Approved HST/Spitzer proposal.