2007/05/31 by Xianzhong Zheng, Xian Zhong Zheng, H. Dole +9
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Galaxies: Formation, Evolution, Phenomena #astro-ph
paper · pdf · doi:10.1086/520529
12 pages, 11 figures, 2 tables, accepted for publication in ApJ
arxiv created 2007/05/31 · openalex publication_date 2007/11/20 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
We analyze the infrared (IR) spectral energy distributions (SEDs) for 10 μm < λ rest < 100 μm for ~600 galaxies at z ~ 0.7 in the extended Chandra Deep Field South by stacking their Spitzer 24, 70, and 160 μm images. We place interesting constraints on the average IR SED shape in two bins: the brightest 25% of z ~ 0.7 galaxies detected at 24 μm, and the remaining 75% of individually detected galaxies. Galaxies without individual detections at 24 μm were not well detected at 70 and 160 μm even through stacking. We find that the average IR SEDs of z ~ 0.7 star-forming galaxies fall within the diversity of z ~ 0 templates. While dust obscuration L IR / L UV seems to be only a function of star formation rate (SFR; ~ L IR + L UV ), not of redshift, the dust temperature of star-forming galaxies (with SFR ~ 10 M ☉ yr -1 ) at a given IR luminosity was lower at z ~ 0.7 than today. We suggest an interpretation of this phenomenology in terms of dust geometry: intensely star-forming galaxies at z ~ 0 are typically interacting, and host dense centrally concentrated bursts of star formation and warm dust temperatures. At z ~ 0.7, the bulk of intensely star-forming galaxies are relatively undisturbed spirals and irregulars, and we postulate that they have large amounts of widespread lower density star formation, yielding lower dust temperatures for a given IR luminosity. We recommend which IR SEDs are most suitable for modeling intermediate-redshift galaxies with different SFRs.