Jason Melbourne

Title: Black Hole Growth and Star Formation in z=2 Dust Obscured Galaxies (DOGs)

Abstract: The appearance at z=2 of ultra-luminous infrared galaxies
(ULIRGs) with number densities and clustering similar to the massive
ellipicals of today, suggests that z=2 may have been a period of rapid
stellar mass and/or black hole growth in massive galaxies.  We have
obtained high spatial resolution (0.1") Keck OSIRIS integral field
spectroscopy of 4 high-z ULIRGs selected to have extreme optical to
mid-IR colors, R - [24] > 14.  Galaxies selected this way are termed
dust obscured galaxies or DOGs.  In each system, we targeted the
H-alpha line redshifted into the near-IR.  The observations spatially
separate the broad-line nuclear region, powered by AGN and star
formation, from the extended (>1 kpc) narrow H-alpha emitting regions
excited by star formation alone.  The four DOGs in our sample are AGN
dominated, and the star formation rates estimated from the narrow
H-alpha lines are an order magnitude lower than for submm-galaxies,
and other star formation dominated ULIRGs.  Compared with local AGN,
estimates of the black hole masses of the DOGs are an order of
magnitude low given their dust corrected galaxy luminosities. These
results can be partially explained if the DOGs are near the end of a
starburst phase where AGN black hole growth has begun to shut down
star formation.