AAS 205th Meeting, 9-13 January 2005
Session 94 From Protogalaxies to Large Surveys: Tracing the Galaxy Evolution
Poster, Wednesday, January 12, 2005, 9:20am-6:30pm, Exhibit Hall

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[94.01] Probing the Physical Properties of High Redshift Optically Obscured Galaxies in the Bootes NOAO Deep Wide Field Survey using the Infrared Spectrograph on Spitzer

S. J. U. Higdon, D. Weedman, J. L. Higdon, J. R. Houck (Cornell University), B. T. Soifer, L. Armus (California Institute of Technology), V. Charmandaris, T. L. Herter (Cornell University), B. R. Brandl (Leiden Observatory), M. J. I. Brown (Princeton University), A. Dey, B. Jannuzi (National Optical Astronomy Observatory), E. Le Floc'h, M. Rieke (Steward Observatory)

We have surveyed a field covering 8.4 degrees2 within the NOAO Deep Wide Field Survey region in Boötes with the Multiband Imaging Photometer on the Spitzer Space Telescope to a limiting 24 um flux density of 0.3 mJy, identifying ~ 22,000 point sources. Thirty one sources from this survey with F(24 um) > 0.75 mJy , which are optically ``invisible'' (R > 26) or very faint (I > 24) have been observed with the low-resolution modules of the Infrared Spectrograph on SST.

The spectra were extracted using the IRS SMART spectral analysis package in order to optimize their signal to noise. A suite of mid-IR spectral templates of well known galaxies, observed as part of the IRS GTO program, is used to perform formal fits to the spectral energy distribution of the Boötes sources. These fits enable us to measure their redshift, to calculate the depth of the 9.7 um silicate feature along with the strength of 7.7 um PAH, as well as to estimate their bolometric luminosities. We compare the mid-IR slope, the measured PAH luminosity, and the optical depth of these sources with those of galaxies in the local Universe. As a result we are able to estimate the contribution of a dust enshrouded active nucleus to the mid-IR and bolometric luminosity of these systems.

This work is based [in part] on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407. Support for this work was provided by NASA through Contract Number 1257184 issued by JPL/Caltech.

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