Spitzer Mid- to Far-Infrared Flux Densities of Distant Galaxies**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. Academic Article uri icon


  • We study the infrared (IR) properties of high-redshift galaxies using deep Spitzer 24, 70, and 160 m 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 m flux densities of 1.5 < z < 2.5 galaxies as a function of 24 m flux density, X-ray activity, and rest-frame near-IR color. Galaxies with 1.5 < z < 2.5 and S 24 = 53-250 Jy have L IR derived from their average 24-160 m flux densities within factors of 2-3 of those inferred from the 24 m flux densities only. However, L IR derived from the average 24-160 m flux densities for galaxies with S 24 > 250 Jy and 1.5 < z < 2.5 are lower than those inferred using only the 24 m flux density by factors of 2-10. Galaxies with S 24 > 250 Jy 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 m emission. Based on the average 24-160 m flux densities, nearly all 24 m-selected galaxies at 1.5 < z < 2.5 have L IR < 6 10 12 L , which, if attributed to star formation, corresponds to < 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. 2007. The American Astronomical Society. All rights reserved.

published proceedings

  • The Astrophysical Journal

author list (cited authors)

  • Papovich, C., Rudnick, G., Le Floch, E., van Dokkum, P. G., Rieke, G. H., Taylor, E. N., ... Franx, M.

citation count

  • 149

complete list of authors

  • Papovich, Casey||Rudnick, Gregory||Le Floc’h, Emeric||van Dokkum, Pieter G||Rieke, George H||Taylor, Edward N||Armus, Lee||Gawiser, Eric||Huang, Jiasheng||Marcillac, Delphine||Franx, Marijn

publication date

  • October 2007