Spectroscopic redshifts to z > 2 for optically obscured sources discovered with the spitzer space telescope

J. R. Houck, B. T. Soifer, D. Weedman, S. J.U. Higdon, J. L. Higdon, T. Herter, M. J.I. Brown, A. Dey, B. T. Jannuzi, E. L.E. Floc'h, M. Rieke, L. Armus, V. Charmandaris, B. R. Brandl, H. I. Teplitz

Research output: Contribution to journalArticlepeer-review

195 Scopus citations


We have surveyed a field covering 9.0 deg2 within the NOAO Deep Wide-Field Survey region in Bootes with the Multiband Imaging Photometer on the Spitzer Space Telescope (SST) to a limiting 24 μm flux density of 0.3 mJy. Thirty-one sources from this survey with F24μm > 0.75 mJy that are optically very faint (R ≳ 24.5 mag) have been observed with the low-resolution modules of the Infrared Spectrograph on SST (IRS). Redshifts derived primarily from strong silicate absorption features are reported here for 17 of these sources; 10 of these are optically invisible (R ≳ 26 mag), with no counterpart in BW, R, or I. The observed redshifts for 16 sources are 1.7 < z < 2.8. These represent a newly discovered population of highly obscured sources at high redshift with extreme infrared-to-optical ratios. Using IRS spectra of local galaxies as templates, we find that a majority of the sources have mid-infrared spectral shapes most similar to ultraluminous infrared galaxies powered primarily by active galactic nuclei. Assuming that the same templates also apply at longer wavelengths, bolometric luminosities exceed 1013 L⊙.

Original languageEnglish (US)
Pages (from-to)L105-L108
JournalAstrophysical Journal
Issue number2 II
StatePublished - Apr 1 2005


  • Dust, extinction
  • Galaxies: Active
  • Galaxies: High
  • Galaxies: Starburst
  • Infrared: Galaxies
  • Redshift

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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