PI: Philip R. Maloney, University of Colorado, email@example.com
Address: Center for Astrophysics and Space Astronomy, Boulder, CO 80309-0839, U.S.A.
CoI: Chris Dudley, Naval Research Laboratory
CoI: Masatoshi Imanishi, National Astronomical Observatory of Japan
Title: Buried AGN in Ultraluminous Infrared Galaxies
Abstract: Ultraluminous infrared galaxies (ULIRGs) have been used extensively to trace the star formation history in the early universe. However, our current understanding of these galaxies is still incomplete. A major issue is determining the energetic importance of elusive \it buried AGN at the cores of the ~ 70% of ULIRGs with no optical evidence for AGN. This has been hampered in previous studies, because of: (1) high nuclear extinctions (A_V\gg 1); (2) serious difficulty in distinguishing buried AGN from starbursts; and (3) strong spectral contamination from energetically unimportant, weakly extinguished, extended starbursts. 3-4 (micron) slit spectroscopy offers a powerful probe of compact, buried energy sources, because: (1) we have diagnostic tools to distinguish starbursts and AGN, (2) dust extinction is sufficiently low and the contribution from AGN-powered emission to an observed 3-4 (micron) flux is sufficiently large that a buried AGN is detectable even at A_V\gg 1, and, most importantly, (3) the dereddened AGN luminosity is best quantified using 3-4 (micron) data, even if the opacity is > 1 at 3-4 (mu)m. Our pilot program has succeeded in detecting the clear signatures of buried AGN (up to A_V ~ 150 mag) and quantifying their contributions in several non-Seyfert ULIRGs. We plan to extend this successful approach to a statistically significant number of non-Seyfert ULIRGs to investigate whether energetically important, buried AGN are common in ULIRGs.
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