Spitzer Space Telescope - Guaranteed Time Observer Proposal #40537


IRS Observation of IR luminous LBGs

Principal Investigator: Giovanni Fazio
           Institution: Smithsonian Astrophysical Observatory

     Technical Contact: Jiasheng Huang, Smithsonian Astrophysical Observatory

Co-Investigators: 
Dimitra Rigopoulou, Oxford                                            
Lin Yan, SSC                                                          
Tracy Webb, McGill University                                         
Matt Ashby, SAO                                                       
Steve Willner, SAO                                                    
Casey Papovich, U Arizona                                             
Delphine Marcillac, U Arizona                                         

Science Category: high-z galaxies (z>0.5) 
 Observing Modes: IrsMap IrsPeakupImage 
  Hours Approved: 47.3 

Abstract:
Lyman-Break Galaxies (LBGs) and Submillimeter Galaxies (SMGs) are star-forming
galaxies at high-redshifts, selected in very different ways. A large amount of
spectroscopic data are now available for LBGs, and consequently we have an
increasingly meaninful understanding of their physical properties. By contrast
SMGs (i.e., high-redshift ULIRGs) are notoriously faint and difficult to
identify at visible wavelengths, making it extremely hard even to measure their
redshifts. However, we have recently discovered (Huang etal 2005) a population
that links LBGs and SMGs: Infrared-Luminous Lyman Break Galaxies (ILLBGs).
ILLBGs strongly resemble SMGs in the infrared, yet are surprisingly bright at
visible wavelengths. This permits 1.) high S/N study of their rest-frame UV
spectra, 2.) measurement of differences in physical properties between normal
blue LBGs and ILLBGs, and 3.) comparison of ILLBGs to their local ULIRG/LIRG
couterparts. We have recently completed a new, large photometric survey for LBGs
in the Extended Groth Strip (EGS) field, in which we detected 6500 LBG
candidates. Amoung these, 220 have clear detections in the MIPS 24 micron band
-- in other words, they are ILLBGs. This is the largest ULIRG/LIRG sample at z=3
in existence. We ask for four nights of GMOS time to carry out a spectroscopic
study of this important population that links LBGs and SMGs.