Spitzer Mid‐ to Far‐Infrared Flux Densities of Distant Galaxies Academic Article uri icon

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 L IR 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, L IR 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. © 2007. The American Astronomical Society. All rights reserved.

author list (cited authors)

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

citation count

  • 144

publication date

  • October 2007