AAS 205th Meeting, 9-13 January 2005
Session 163 New Results from the Great Observatories Origins Deep Survey
Special Session, Thursday, January 13, 2005, 2:00-3:30pm, Town and Country

Previous   |   Session 163   |   Next

[163.09] Spectral Energy Distributions of X-ray Selected Sources in the GOODS Field: Revealing Highly-Obscured AGN

J. Van Duyne, C.M. Urry, E. Chatzichristou, E. Treister (Yale University), M. Dickinson (NOAO), F.E. Bauer (IoA Cambridge), N.A. Grogin (JHU), V. Laidler, B. Mobasher, A. Koekemoer (STScI), B. Simmons (Yale University), GOODS Team

We present infrared through X-ray spectral energy distributions (SEDs) of the 198 hard X-ray selected, z-band identified, active galactic nuclei (AGNs) from the GOODS multiwavelength survey. These SEDs include photometry from Spitzer/IRAC observations. Fits to the optical/IR SEDs with local empirical SED templates of both normal and active galaxies identify 36 Type 1 AGN, 89 Type 2 AGN, 64 early-type galaxies and 9 late-type spiral galaxies. Because the majority of the ``early-type galaxies'' are strong X-ray sources with high X-ray hardness ratios and strong infrared emission, they likely harbor fully obscured nuclear activity. Assuming a 15% contamination factor of starbursts in the Type 2 classification, the ratio of obscured to unobscured AGN in our sample is ~3.7:1 for the full redshift range of 0.3 < z < 3.7, and ~4.1:1 for 0.5 < z < 2, which contains 62% of the sample and is relatively complete. We observe a decline in this ratio at z > 2, but these values are suspect due to low number statistics and reliance on photometric redshifts due to the R < 24 spectroscopic cutoff.

We compare NH column densities as obtained from model SED fits with predicted distributions (Treister et al. 2004), as well as comparing optical morphology classifications to the observed SEDs. Color-color diagrams of IRAC bands and bolometric luminosity estimates demonstrate the utility of using Spitzer to identify high redshift, moderate luminosity, highly-obscured AGN. Due to the breadth of wavelength coverage, the depth of the images, and precision of source positions, the present sample constitiues one of the largest, least-biased AGN samples to date, representative of the true AGN population.

The author(s) of this abstract have provided an email address for comments about the abstract: vanduyne@astro.yale.edu

Previous   |   Session 163   |   Next

Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.