29 March 2007

Speaker: David Sanders (University of Hawaii)

Title: The Origin and Evolution of Luminous Infrared Galaxies: new results from the Spitzer-COSMOS survey.

Abstract: New multi-wavelength studies of complete samples of luminous infrared galaxies (LIGs) in the local universe confirm that strong interactions/mergers of gas-rich spirals provide the trigger for the intense infrared luminosity, and that the most luminous objects are intimately related to intense nuclear starbursts and the the rapid growth of super massive black holes. The Spitzer-COSMOS survey of the HST-ACS 2sqdeg field is designed to extend the detailed multi-wavelength studies of LIGs out to higher redshifts, and more generally, to provide an infrared view of galaxies for comparison with that seen in the optical. Early science results from S-COSMOS suggest that the deep optical surveys have indeed missed an important class of extragalactic objects ! S-COSMOS MIPS-24 results clearly reveal a substantial population of infrared luminous galaxies which fill the optical "green valley" . These infrared selected objects appear to provide a plausible evolutionary connection between galaxies in the "blue cloud" (starburst disks) and "red sequence" (old stars/ellipticals) -- the bimodal distribution which characterizes the extragalactic population seen in the optical.

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