signature=2dfd4e6ee943f204c0501ff860a06184,NICMOS Imaging of the z ~ 2 Spitzer Spectroscopic Sample ...

Abstract

We propose to obtain NICMOS images of the first large sample of high-z ultra-luminous infrared galaxies {ULIRGs} whose redshifts and physical states have been determined with Spitzer mid-IR spectra. The detection of strong silicate absorption and/or PAH emission lines suggest that the these sources are a mixture of highly obscured starbursts, AGNs and composite systems at z=2. Although some of the spectra show PAH emission similar to local starburst ULIRGs, their bolometric luminosities are roughly an order of magnitude higher. One important question is if major mergers, which are the trigger for 95% of local ULIRGs, also drive this enormous energy output observed in our z=2 sample. The NICMOS images will allow us to {1} measure surface brightness profiles of z 2 ULIRGs and establish if major mergers could be common among our luminous sources at these early epochs, {2} determine if starbursts and AGNs classified based on their mid-IR spetra would have different morphological signatures, thus different dynamic state; {3} make comparisons with the similar studies of ULIRGs at z 0 - 1, thus infer any evolutionary connections between high-z ULIRGs and the formation of normal, massive galaxies and quasars observed today.