Casey, Caitlin M.Zavala, Jorge A.Spilker, Justinda Cunha, ElisabeteHodge, JacquelineHung, Chao-LingStaguhn, JohannesFinkelstein, Steven L.Drew, Patrick2020-07-082020-07-080004-637Xhttp://hdl.handle.net/1885/205942Though half of cosmic starlight is absorbed by dust and reradiated at long wavelengths (3 μm–3 mm), constraints on the infrared through the millimeter galaxy luminosity function (or the "IRLF") are poor in comparison to the rest-frame ultraviolet and optical galaxy luminosity functions, particularly at z gsim 2.5. Here, we present a backward evolution model for interpreting number counts, redshift distributions, and cross-band flux density correlations in the infrared and submillimeter sky, from 70 μm–2 mm, using a model for the IRLF out to the epoch of reionization. Mock submillimeter maps are generated by injecting sources according to the prescribed IRLF and flux densities drawn from model spectral energy distributions that mirror the distribution of SEDs observed in 0 < z < 5 dusty star-forming galaxies (DSFGs). We explore two extreme hypothetical case studies: a dust-poor early universe model, where DSFGs contribute negligibly (<10%) to the integrated star formation rate density at z > 4; and an alternate dust-rich early universe model, where DSFGs dominate ~90% of z > 4 star formation. We find that current submm/mm data sets do not clearly rule out either of these extreme models. We suggest that future surveys at 2 mm will be crucial to measuring the IRLF beyond z ~ 4. The model framework developed in this paper serves as a unique tool for the interpretation of multiwavelength IR/submm extragalactic data sets, and will enable more refined constraints on the IRLF than can be made from direct measurements of individual galaxies' integrated dust emission.The Aspen Center for Physics is supported by National Science Foundation grant PHY-1066293. C.M.C. thanks the National Science Foundation for support through grant AST1714528. Additionally, C.M.C. and J.A.Z. thank the University of Texas at Austin College of Natural Sciences for support. J.S. thanks the McDonald Observatory at the University of Texas at Austin for support through a Smith Fellowship. E.dC. gratefully acknowledges the Australian Research Council for funding support as the recipient of a Future Fellowship (FT150100079). J.A.H. acknowledges support of the VIDI research programme with project number 639.042.611, which is (partly) financed by the Netherlands Organisation for Scientific Research (NWO). S.L.F. acknowledges support from an NSF AAG award AST-1518183.application/pdfen-AU© 2018 The American Astronomical Societygalaxies: evolutiongalaxies: starburstsubmillimeter: galaxies2018-07-2510.3847/1538-4357/aac82d2020-06-23