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A SPITZER UNBIASED ULTRADEEP SPECTROSCOPIC SURVEY

TitleA SPITZER UNBIASED ULTRADEEP SPECTROSCOPIC SURVEY
Publication TypeJournal Article
Year of Publication2009
AuthorsBertincourt, B, Helou, G, Appleton, P, Ogle, P, Lagache, G, Brooke, T, Smith, JD, Sheth, K, Dale, D, Harwit, M, Puget, JL, Roussel, H
JournalAstrophysical Journal
Volume705
Pagination68-88
Date PublishedNov
ISBN Number0004-637X
Accession NumberWOS:000270903200007
Abstract

We carried out an unbiased, spectroscopic survey using the low-resolution module of the infrared spectrograph (IRS) onboard Spitzer targeting two 2.6 square arcminute regions in the GOODS-North field. The IRS was used in a spectral mapping mode with 5 hr of effective integration time per pixel. One region was covered between 14 and 21 mu m and the other between 20 and 35 mu m. We extracted spectra for 45 sources. About 84% of the sources have reported detections by GOODS at 24 mu m, with a median f(nu)( 24 mu m) similar to 100 mu Jy. All but one source are detected in all four IRAC bands, 3.6 to 8 mu m. We use a new cross-correlation technique to measure redshifts and estimate IRS spectral types; this was successful for similar to 60% of the spectra. Fourteen sources show significant polycyclic aromatic hydrocarbon emission, four mostly SiO absorption, eight present mixed spectral signatures (low PAH and/or SiO) and two show a single line in emission. For the remaining 17, no spectral features were detected. Redshifts range from z similar to 0.2 to z similar to 2.2, with a median of 1. IR luminosities are roughly estimated from 24 mu m flux densities, and have median values of 2.2 x 10(11)L(circle dot) and 7.5 x 10(11)L(circle dot) at z similar to 1 and z similar to 2, respectively. This sample has fewer active galactic nuclei than previous faint samples observed with the IRS, which we attribute to the fainter luminosities reached here.

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