Spitzer Space Telescope - General Observer Proposal #80156 Spitzer Imaging of Herschel Lensed Sub-mm Galaxies Principal Investigator: Asantha Cooray Institution: University of California Irvine Technical Contact: Asantha Cooray, University of California Irvine Co-Investigators: Julie Wardlow, UC Irvine Sam Kim, UC Irvine Ali Khostovan, UC Irvine Ketron Mitchell-Wynne, UC Irvine Elizabeth Barton, UC Irvine Yan Gong, UC Irvine Alexandre Amblard, NASA Ames Paolo Serra, NASA Ames Jeff Cooke, Caltech Dominik Riechers, Caltech Benford Dominic, NASA Goddard David Frayer, NOAO Jonathan Gardner, NASA Goddard Hai Fu, Caltech Shane Bussmann, Harvard/CfA Mark Gurwell, Harvard/CfA Lerothodi Leeuw, SETI Institute Temi Pasquale, NASA Ames Alex Conley, Colorado Jamie Bock, Caltech Joaquin Vieira, Caltech Carrie Bridge, Caltech Jason Glenn, Colorado Michael Zemcov, Caltech Bernhard Schulz, Caltech David Shupe, IPAC Ros Hopwood, Imperial Mattia Negrello, Open U, UK Paola Andreani, ESO David Clements, Imperial Helmut Dannerbauer, CEA, France Gianfranco De Zotti, Padova Loretta Dunne, U. of Nottingham James Dunlop, Edinburgh Steve Eales, Cardiff University Duncan Farrah, Sussex Rob Ivison, Edinburgh Matt Jarvis, Herts Steve Maddox, Nottingham Michal Michalowski, Edinburgh Alain Omont, IAP, France Ismael Perez-Fournon, IAC, Spain Dimitra Rigopoulou, Oxford Stephen Serjeant, Open U Ian Smail, Durham Mark Thompson, Herts Mattia Vaccari, Padova Aprajita Verma, Oxford Kirsten Coppin, McGill Seb Oliver, Sussex Lingyu Wang, Sussex Science Category: ULIRGS/LIRGS/HLIRGS Observing Modes: IRAC Post-Cryo Mapping Hours Approved: 93.6 Abstract: Sub-millimeter surveys have, in the last decade, revealed an unexpected population of high-redshift dust-obscured sub-mm galaxies (SMGs) which are forming stars at a tremendous rate. Due to steep number counts and the negative k-correction at sub-mm wavelengths sub-mm surveys are effective at finding intrinsically faint, gravitationally lensed galaxies. We have now produced a reliable list of about 150 bright lensed SMGs in 200 sq. deg of the Herschel-ATLAS and HerMES (the GTO program of the SPIRE Instrument team) surveys with Herschel-SPIRE. We propose Spitzer IRAC 3.6 and 4.5 micron imaging of 122 of these gravitationally lensed SMGs. The target SMGs are selected to maximally overlap with existing and planned multi-wavelength followup programs, without duplicating existing deep IRAC data. Using the proposed Spitzer data we will: (a) Extend the SEDs of z~ 1 to 5 lensed SMGs into the near-IR regime, where derived stellar masses are more reliable than those estimated at other wavelengths alone; (b) Combine with lens models from existing and planned high-resolution sub-mm imaging (SMA, CARMA, PdBI) to map the evolution of stellar mass as a function of redshift and star-formation rate (SFR); (c) Combine with existing and planned CO and CII molecular line measurements to map the evolution of dust-to-gas and stellar-to-gas mass ratios as a function of redshift and SFR; (d) Obtain snapshot statistics on the sub-mm galaxy evolution from z of 1 to 5 as a function of stellar, dust, and gas mass to study the role of mergers and AGN contribution that may regulate the starburst phenomenon; (e) Compare our results to those from numerical simulations of high-redshift starburst galaxies to investigate the physical conditions in SMGs, and their evolutionary pathways.