科研之友
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摘要
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.
- 出版日期2009-11-1
