Spitzer Space Telescope - General Observer Proposal #20216


A bridge between ultraluminous and normal galaxies at high redshifts:
Spitzer imaging of a unique spectroscopic radio field

Principal Investigator: Andrew Blain
           Institution: Caltech

Co-Investigators: 
Scott Chapman, Caltech                                                
Ian Smail, University of Durham                                       
Lee Armus, Caltech/SSC                                                
David Frayer, Caltech/SSC                                             
David Alexander, University of Cambridge                              
Rob Ivison, UKATC                                                     

Science Category: ULIRGS/LIRGS/HLIRGS 
 Observing Modes: IracMap MipsPhot 
  Hours Approved: 13.3 

Abstract:
Ultradeep radio images and Spitzer maps both provide windows on the
high-redshift Universe immune to the effects of dust extinction.  The
very deepest radio sources trace the evolution of star-formation
activity at luminosities less than the confusion limit in submm and
far-IR surveys, opening a bridge between the most extreme
submm-selected galaxies and the optically-selected Lyman-break
population:  the galaxies at 100-1000  Giga solar luminosities that
dominate the far-IR background.  We are targeting a VLA image in the
Lockman Hole that goes twice as deep as the GOODS-N radio map for
complete spectroscopy of the 250  radio sources to build up a compact,
densely-sampled 15-arcmin field.  These spectra will yield an
unparalleled view of both the rate of evolution and the large-scale
structure traced by dust-obscured galaxies.  Spitzer IRAC and MIPS
imaging of this special field will allow an unprecedented census of
the rate and spatial distribution of dust-enshrouded high-redshift
star formation activity, with MIPS revealing details of the galaxy
SEDs, and the relationship between radio and far-IR emission, while
IRAC reveals the stellar masses built up in the dust-enshrouded
galaxies that could provide the link between current optical and
far-IR samples, and which make most of the stars in the Universe
today.