Caitlin Casey

Title: Taking Census of Extreme, Infrared-Bright Starbursts from z=0-6:
Implications for Dust Enshrouded Star Formation and the Evolution of Major Mergers

Abstract: Ultraluminous Infrared Galaxies (ULIRGs) exhibit the most extreme episodes of star formation in the Universe.  They contribute significantly to the buildup of stellar mass over 10 billion years of cosmic time (~>50%) and are the likely progenitors to massive, elliptical galaxies in the local Universe.  Despite their importance in galaxy evolution, much about this extreme starbursting population is unknown due to their intrinsically dusty nature and limitations in FIR data.  Recent work has suggested that extreme starbursts in the local Universe differ greatly with those at z~2, where the former are dominated by major mergers of disk galaxies and the latter are dominated by gas-rich spirals.  Other groups suggest the majority of z~2 ULIRGs at major merger dominated.  Work from the rest-frame UV out to z~8 suggest that, in fact, the IR contribution to the buildup of stellar mass is minimal, yet constrained FIR measurements at these redshifts are almost non-existant.

In this talk I will discuss my recent work in:
  (a) taking census of IR-bright starbursts from z=0-6 through a Keck spectroscopic program at the IfA.  I will describe an ambitious survey underway using Keck LRIS and DEIMOS to spectroscopically confirm redshifts for >500 Herschel SPIRE-detected (250, 350, and 500um detected) galaxies.  I measure FIR SEDs for each galaxy, estimate their evolving luminosity function, and their contribution to the cosmic star formation rate density and reflect on other measurements in the literature, from other IR estimates (so far limited to z<1) and from UV estimates out to z~6.  I also discuss the relative selection of SPIRE-detected galaxies against previously well-studied SMGs which are 850um detected by SCUBA.
     ...and...
  (b) ongoing efforts of characterize the nature of z~2 ULIRG activity through multiwavelength diagnostics.  This includes a large multi-year PdBI program pursuing CO detection in z~2 SMGs, analyzing their gas excitation and resolved kinematics, mid-IR spectroscopic programs completed by Spitzer, X-ray analysis, and resolved Halpha kinematic maps from Keck-OSIRIS/VLT-SINFONI/Gemini-NIFS.  These multiwavelength diagnostics allow the complete physical characterization of high-z starbursts, and begin to answer questions on the merger frequency, gas fractions, star formation histories and AGN fraction which shed light on galaxy evolution theories in the high-z Universe.