Infrared spectral energy distributions of z ∼ 0.7 star-forming galaxies

We analyze the infrared ( IR) spectral energy distributions ( SEDs) for 10 mu m < lambda(rest) < 100 mu m for similar to 600 galaxies at z similar to 0.7 in the extended Chandra Deep Field South by stacking their Spitzer 24, 70, and 160 mu m images. We place interesting constraints on the average IR SED shape in two bins: the brightest 25% of z similar to 0.7 galaxies detected at 24 mu m, and the remaining 75% of individually detected galaxies. Galaxies without individual detections at 24 mu m were not well detected at 70 and 160 mu m even through stacking. We find that the average IR SEDs of z similar to 0.7 star- forming galaxies fall within the diversity of z similar to 0 templates. While dust obscuration L-IR/L-UV seems to be only a function of star formation rate (SFR; similar to L-IR + L-UV), not of redshift, the dust temperature of star- forming galaxies ( with SFR similar to 10 M-circle dot yr(-1)) at a given IR luminosity was lower at z similar to 0.7 than today. We suggest an interpretation of this phenomenology in terms of dust geometry: intensely star- forming galaxies at z similar to 0 are typically interacting, and host dense centrally concentrated bursts of star formation and warm dust temperatures. At z similar to 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.