Virginia TechLo Faro, B.Franceschini, A.Vaccari, M.Silva, L.Rodighiero, G.Berta, S.Bock, J.Burgarella, D.Buat, V.Cava, A.Clements, D. L.Cooray, A.Farrah, D.Feltre, A.Solares, E. A. G.Hurley, P.Lutz, D.Magdis, G. E.Magnelli, B.Marchetti, L.Oliver, S. J.Page, M. J.Popesso, P.Pozzi, F.Rigopoulou, D.Rowan-Robinson, M.Roseboom, I. G.Scott, D.Smith, A. J.Symeonidis, M.Wang, L.Wuyts, S.2014-02-252014-02-252013-01B. Lo Faro et al. 2013. "The Complex Physics of Dusty Star-Forming Galaxies at High Redshifts as Revealed by Herschel and Spitzer," ApJ 762 108 doi:10.1088/0004-637X/762/2/1080004-637Xhttp://hdl.handle.net/10919/25552We combine far-infrared photometry from Herschel (PEP/HerMES) with deep mid-infrared spectroscopy from Spitzer to investigate the nature and the mass assembly history of a sample of 31 luminous and ultraluminous infrared galaxies ((U)LIRGs) at z similar to 1 and 2 selected in GOODS-S with 24 mu m fluxes between 0.2 and 0.5 mJy. We model the data with a self-consistent physical model (GRASIL) which includes a state-of-the-art treatment of dust extinction and reprocessing. We find that all of our galaxies appear to require massive populations of old (>1 Gyr) stars and, at the same time, to host a moderate ongoing activity of star formation (SFR <= 100 M-circle dot yr(-1)). The bulk of the stars appear to have been formed a few Gyr before the observation in essentially all cases. Only five galaxies of the sample require a recent starburst superimposed on a quiescent star formation history. We also find discrepancies between our results and those based on optical-only spectral energy distribution (SED) fitting for the same objects; by fitting their observed SEDs with our physical model we find higher extinctions (by Delta A(V) similar to 0.81 and 1.14) and higher stellar masses (by Delta log(M-*) similar to 0.16 and 0.36 dex) for z similar to 1 and z similar to 2 (U)LIRGs, respectively. The stellar mass difference is larger for the most dust-obscured objects. We also find lower SFRs than those computed from LIR using the Kennicutt relation due to the significant contribution to the dust heating by intermediate-age stellar populations through "cirrus" emission (similar to 73% and similar to 66% of the total L-IR for z similar to 1 and z similar to 2 (U)LIRGs, respectively).en-USIn Copyrightgalaxies: evolutiongalaxies: generalgalaxies: interactionsgalaxies: starburstspectral energy-distributionluminous infrared galaxiessimilar-to 1starburst galaxiessubmillimeter galaxiesradiative-transferevolutiondistributionsemissionmodelsArticle - Refereedhttp://iopscience.iop.org/0004-637X/762/2/108/pdf/0004-637X_762_2_108.pdfhttps://doi.org/10.1088/0004-637x/762/2/108