Spectroscopic Redshifts to z > 2 for Optically Obscured Sources Discovered with the Spitzer Space Telescope
Abstract
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 Lsolar.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 2005
- DOI:
- 10.1086/429405
- arXiv:
- arXiv:astro-ph/0502216
- Bibcode:
- 2005ApJ...622L.105H
- Keywords:
-
- ISM: Dust;
- Extinction;
- Galaxies: Active;
- Galaxies: High-Redshift;
- Galaxies: Starburst;
- Infrared: Galaxies;
- Astrophysics
- E-Print:
- Accepted for publication on 7 Feb 2005 in ApJL. 7 pages 2 figures