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Paper: The Cosmic History of Star Formation from Spitzer Observations
Volume: 446, Galaxy Evolution: Infrared to Millimeter Wavelength Perspective
Page: 3
Authors: Rieke, G. H.; Rujopakarn, W.
Abstract: At high redshifts (z = 0.5 to 2.5), the spectral energy distributions of infrared-luminous galaxies shift toward relatively more output in the aromatic bands and more output at the longer far infrared wavelengths, compared with local galaxies of the same luminosities. To first order, this shift arises because the star forming regions in the high redshift galaxies are substantially more extended (diameters of 3 - 7 kpc) than those of local LIRGs and ULIRGs (< 1 kpc). A simple correction based on this hypothesis allows use of 24 μm observations to estimate L(TIR) to within 0.1 dex on average, and with rms scatter of only ∼ 0.2 dex. This success confirms that extended star forming regions are the rule (a significant admixture of compact cases similar to the local galaxies would result in far larger scatter in the predictions). Thus, if luminous galaxies result from mergers at high redshift, the behavior must be different from local mergers - the interaction must trigger star formation over the entire galaxy, not just in gas collected tightly around the nucleus of the merger product. Alternatively, star formation in some of these galaxies may arise spontaneously. Our procedure allows estimating L(TIR) in large numbers of galaxies; we find evidence that the maximum luminosity associated with star formation is likely not to exceed 1013 L. Finally, the ability to determine accurate L(TIR)s and SFRs from mid-infrared measurements will allow JWST to advance substantially our understanding of star formation in the critical 1 < z < 2.5 range.
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