IR Spectral Diagnostics of z=2 Dust Obscured Galaxies (DOGs) Jason Melbourne (Caltech) B.T. Soifer, Lee Armus, Keith Matthews, Vandana Desai, Arjun Dey, Shane Bussmann Melbourne et al. 2008

DOGs are Defined by Very Red Optical to Mid-IR Colors R-[24] > 14 (Vega mag) F [24] /F [R] > 1000 Significant amounts of warm dust. Total IR energy densities great than ULIRGs. Dey et al. 2008

Over 2000 DOGs Identified in the NOAO Deep Wide Field Survey of Bootes 10 square degrees BRI ground based imaging Spitzer IRAC imaging Spitzer MIPS imaging

The Redshift Distribution of DOGs is Centered About z=2 Median redshift of z = 1.99  z = 0.5 Dey et al. 2008

Spectral Energy Distributions Vary with 24 micron Flux Brighter DOGs tend to show power-law SEDs. Fainter DOGs tend to show a “bump” in the observed mid-IR. Dey et al. 2008

IRS Spectra of Power-Law DOGs Suggest AGN Activity Weedman et al. 2005

IRS Spectra of “Bump” DOGs Suggest Star Formation Desai et al. 2009

TripleSpec: 5 Orders in the Near-IR, Including J, H, and K in One Spectrum

Spectra of Power-Law DOGs Reveal Broad H  Melbourne et al. in prep H  [nm] z Line width [km/s] HH

Spectra of “Bump” DOGs Reveal Narrow H  Melbourne et al. in prep H  [nm] z Line width [km/s] HH 1 2

Broad Ha from AGN dominates, but narrow Ha suggests star formation  Broad H   Narrow H 

OSIRIS Sample is AGN Dominated

These look different

Summary A simple optical to mid-IR color selection identifies extreme z=2 ULIRGs. These Dust Obscured Galaxies (DOGs) may evolve into massive the ellipticals of today. DOGs are powered by a combination of SF and AGN activity. OSIRIS observations pinpoint the location of the AGN and constrain SFR.

Spectra of Power-Law DOGs Reveal Broad H  Observed Wavelength (  m) Counts