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Spitzer IRS Spectra of Optically Faint Infrared Sources with Weak Spectral Features
The Astrophysical Journal (2006)
  • D. W. Weedman, Cornell University
  • B. T. Soifer, California Institute of Technology
  • Lei Hao, Cornell University
  • J. L. Higdon, Cornell University
  • J. L. Higdon, Cornell University
  • J. R. Houck, Cornell University
  • E. Le Floc'h, University of Arizona
  • M. J. I. Brown
  • A. Dey
  • B. T. Jannuzi
  • M. J. Rieke
  • V. Desai
  • C. Bian
  • D. Thompson
  • L. Armus
  • H. Teplitz
  • P. Eisenhardt
  • S.P. Willner, Smithsonian Astrophysical Observatory
Spectra have been obtained with the low-resolution modules of the Infrared Spectrograph ( IRS) on the Spitzer Space Telescope (Spitzer) for 58 sources having f(24 m) > 0:75 mJy. Sources were chosen from a survey of 8.2 deg2 within the NOAO Deep Wide-Field Survey region in Boo¨tes (NDWFS) using the Multiband Imaging Photometer (MIPS) on Spitzer. Most sources are optically very faint (I > 24 mag). Redshifts have previously been determined for 34 sources, based primarily on the presence of a deep 9.7 m silicate absorption feature, with a median z of 2.2. Spectra are presented for the remaining 24 sources for which we were previously unable to determine a confident redshift because the IRS spectra show no strong features. Optical photometry from the NDWFS and infrared photometry with MIPS and the Infrared Array Camera on Spitzer ( IRAC ) are given, with K photometry from the Keck I telescope for some objects. The sources without strong spectral features have overall spectral energy distributions (SEDs) and distributions among optical and infrared fluxes that are similar to those for the sources with strong absorption features. Nine of the 24 sources are found to have feasible redshift determinations based on fits of a weak silicate absorption feature. Results confirm that the ‘‘1 mJy’’ population of 24 m Spitzer sources that are optically faint is dominated by dusty sources with spectroscopic indicators of an obscured AGN rather than a starburst. There remain 14 of the 58 sources observed in Boo¨tes for which no redshift could be estimated, and 5 of these sources are invisible at all optical wavelengths. 
  • Dust,
  • Extinction,
  • Galaxies,
  • Active,
  • High-redshift,
  • Starburst,
  • Infrared
Publication Date
November 1, 2006
Publisher Statement
This version of the paper was obtained from In order for the work to be deposited in, the author must have copyright or it must be available under the Creative Commons Attribution license,Creative Commons Attribution-Noncommercial-ShareAlike license, orCreate Commons Public Domain Declaration. The publisher's final edited version of this article will be available at The Astrophysical Journal.
Citation Information
Sarah J.U. Higdon, D. W. Weedman, B. T. Soifer, Lei Hao, et al.. "Spitzer IRS Spectra of Optically Faint Infrared Sources with Weak Spectral Features" The Astrophysical Journal Vol. 651 Iss. 1 (2006) p. 101 - 112
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