Astrophys. J., 668, 45-61 (2007/October-2)
Spitzer mid- to far-infrared flux densities of distant galaxies.
PAPOVICH C., RUDNICK G., LE FLOC'H E., VAN DOKKUM P.G., RIEKE G.H., TAYLOR E.N., ARMUS L., GAWISER E., HUANG J., MARCILLAC D. and FRANX M.
Abstract (from CDS):
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, LIR, of these galaxies. We combine the Spitzer data in the southern Extended Chandra Deep Field with a Ks-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 S24=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 S24>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 S24>250 µJy have S70/S24 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 LIR<6x1012 L☉, which, if attributed to star formation, corresponds to Ψ<1000 M☉/yr. This suggests that high-redshift galaxies may have star formation efficiencies and feedback processes similar to those of local analogs. Objects with LIR>6x1012 L☉ are quite rare, with a surface density ∼30±10/deg2, corresponding to ∼2±1x10–6/Mpc3 over 1.5<z<2.5.
Galaxies: High-Redshift - Infrared: Galaxies
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