Spitzer Mid- to Far-Infrared Flux Densities of Distant Galaxies
Abstract
We study the infrared (IR) properties of high-redshift galaxies using deep Spitzer 24, 70, and 160 μm data. Our primary interest is to improve the constraints on the total IR luminosities, L_(IR), of these galaxies. We combine the Spitzer data in the southern Extended Chandra Deep Field with a K_s-band-selected galaxy sample and photometric redshifts from the Multiwavelength Survey by Yale-Chile. We used a stacking analysis to measure the average 70 and 160 μm flux densities of 1.5 < z < 2.5 galaxies as a function of 24 μm flux density, X-ray activity, and rest-frame near-IR color. Galaxies with 1.5 < z < 2.5 and S_(24) = 53-250 μJy have LIR derived from their average 24-160 μm flux densities within factors of 2-3 of those inferred from the 24 μm flux densities only. However, LIR derived from the average 24-160 μm flux densities for galaxies with S_(24) > 250 μJy and 1.5 < z < 2.5 are lower than those inferred using only the 24 μm flux density by factors of 2-10. Galaxies with S_(24) > 250 μJy have S_(70)/S_(24) flux ratios comparable to sources with X-ray detections or red rest-frame IR colors, suggesting that warm dust possibly heated by AGNs may contribute to the high 24 μm emission. Based on the average 24-160 μm flux densities, nearly all 24 μm-selected galaxies at 1.5 < z < 2.5 have L_(IR) < 6 × 10^(12) L_⊙, which, if attributed to star formation, corresponds to Ψ < 1000 M_⊙ yr^(-1). This suggests that high-redshift galaxies may have star formation efficiencies and feedback processes similar to those of local analogs. Objects with L_(IR) > 6 × 10^(12) L_⊙ are quite rare, with a surface density ~30 ± 10 deg^(-2), corresponding to ~2 ± 1 × 10^(-6) Mpc^(-3) over 1.5 < z < 2.5.
Additional Information
© 2007 The American Astronomical Society. Received 2007 February 19; accepted 2007 June 20. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion laboratory, California Institute of Technology, under NASA contract 1407. We wish to thank our collaborators on the MUSYC and MIPS GTO teams for many interesting discussions, and for their much hard work. We also thank the anonymous referee for their suggestions, which improved the quality and clarity of this paper. This work is also based in part on data obtained with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory (JPL), California Institute of Technology (Caltech) under a contract with NASA. Support for this work was provided by NASA through the Spitzer Space Telescope Fellowship Program, through a contract issued by JPL, Caltech under a contract with NASA.Attached Files
Published - PAPapj07.pdf
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Additional details
- Eprint ID
- 16713
- Resolver ID
- CaltechAUTHORS:20091116-094427628
- 1407
- NASA
- NASA Spitzer Fellowship
- Created
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2009-11-25Created from EPrint's datestamp field
- Updated
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2021-11-08Created from EPrint's last_modified field
- Caltech groups
- Infrared Processing and Analysis Center (IPAC)