V. Charmandaris,, L. Armus, H. W. W. Spoon, J. Marshall,V. Desai, B. T. Soifer, and J. R. Houck
PROBING THE PROPERTIES OF ULIRGS WITH THE INFRARED SPECTROGRAPH ON SPITZER

PROBING THE PROPERTIES OF ULIRGS WITH THE INFRARED SPECTROGRAPH ON SPITZER

V. Charmandaris(1,2,3), L. Armus(4), H. W. W. Spoon(2), J. Marshall(2),V. Desai(4), B. T. Soifer(4), and J. R. Houck(2)
(1) University of Crete, Greece
(2) Cornell University, USA
(3) Obs. de Paris, LERMA, France
(4) Spitzer Science Center, Caltech, USA

Ultraluminous Infrared Galaxies (ULIRGs) have power outputs rivalling quasars, yet they emit nearly all of their energy in the mid and far-infrared. Both starbursts and dust-enshrouded AGN have been implicated as the power sources in ULIRGs. While rare in the local Universe, ULIRGs may play a dominant role in producing the far-infrared background as well as the star formation energy density at high redshifts. A large spectroscopic survey of 100 ULIRG with redshifts of 0.02 < z < 0.9 has been performed with the Infrared Spectrograph on Spizter over the 5-35micron range. We will present highlights on the major results from this survey, and discuss their implications on models of cosmological galaxy evolution based on the interpretation of recent mid-IR surveys.