# Far-Infrared Spectral Energy Distributions and Photometric Redshifts of Dusty Galaxies - Astrophysics

Abstract: We infer the large-scale source parameters of dusty galaxies from theirobserved spectral energy distributions SEDs using the analytic radiativetransfer methodology presented in Chakrabarti and McKee 2005. For localultra-luminous infrared galaxies ULIRGs, we show that the millimeter tofar-infrared FIR SEDs can be well fit using the standard dust opacity indexof 2 when self-consistent radiative transfer solutions are employed, indicatingthat the cold dust in local ULIRGs can be described by a single grain model. Wedevelop a method for determining photometric redshifts of ULIRGs and sub-mmgalaxies from the millimeter-FIR SED; the resulting value of $1+z$ is typicallyaccurate to about 10%. As such, it is comparable to the accuracy of near-IRphotometric redshifts and provides a complementary means of deriving redshiftsfrom far-IR data, such as that from the upcoming $\it{Herschel SpaceObservatory}$. Since our analytic radiative transfer solution is developed forhomogeneous, spherically symmetric, centrally heated, dusty sources, it isrelevant for infrared bright galaxies that are primarily powered by compactsources of luminosity that are embedded in a dusty envelope. We discuss howdeviations from spherical symmetry may affect the applicability of oursolution, and we contrast our self-consistent analytic solution with standardapproximations to demonstrate the main differences.

Author: Sukanya Chakrabarti, Christopher F. McKee

Source: https://arxiv.org/