We present a comprehensive investigation of the cosmological evolution of the luminosity function of galaxies and active galactic nuclei (AGN) in the infrared (IR). Based on the observed dichotomy in the ages of stellar populations of early-type galaxies on one side and late-type galaxies on the other, the models interprets the epoch-dependent luminosity functions at z ≥ 1.5 using a physical model for the evolution of proto-spheroidal galaxies and of the associated AGNs, while IR galaxies at z < 1.5 are interpreted as being mostly late-type "cold" (normal) and "warm" (starburst) galaxies. As for proto-spheroids, in addition to the epoch-dependent luminosity functions of stellar and AGN components separately, we have worked out, for the first time, the evolving luminosity functions of these objects as a whole (stellar plus AGN component), taking into account in a self-consistent way the variation with galactic age of the global SED. The model provides a physical explanation for the observed positive evolution of both galaxies and AGNs up to z ≃ 2.5 and for the negative evolution at higher redshifts, for the sharp transition from Euclidean to extremely steep counts at (sub-)mm wavelengths, as well as the (sub-)mm counts of strongly lensed galaxies, that are hard to account for by alternative, physical or phenomenological, approaches. The evolution of late-type galaxies and of z < 1.5 AGNs is described using a parametric phenomenological approach. The modeled AGN contributions to the counts and to the cosmic infrared background (CIB) are always subdominant. They are maximal at mid-IR wavelengths: the contribution to the 15 and 24 µm counts reaches 20% above 10 and 2 mJy, respectively, while the contributions to the CIB are of 8.6% and of 8.1% at 15 µm and 24 µm, respectively. The model provides a good fit to the multi-wavelength (from the mid-IR to millimeter waves) data on luminosity functions at different redshifts and on number counts (both global and per redshift slices). A prediction of the present model, useful to test it, is a systematic variation with wavelength of the populations dominating the counts and the contributions to the CIB intensity. This implies a specific trend for cross-wavelength CIB power spectra, that is found to be in good agreement with the data.

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Citation for published item:svisonD FtF nd vewisD eFtFF nd eissD eF nd erumugmD F nd impsonD tFwF nd rollndD FF nd wddoxD F nd hunneD vF nd linteD iF nd vn der erfD F nd ymontD eF nd hnneruerD rF nd milD sF nd fertoldiD pF nd fremerD wF nd fussmnnD FF nd giD FEF nd glementsD hFvF nd gooryD eF nd he ottiD qF nd ilesD FeF nd pullerD gF nd qonzlezExuevoD tF nd srD iF nd xegrelloD wF nd yteoD sF nd ¡ erezEpournonD sF nd iehersD hF nd tevensD tFeF nd winnkD eFwF nd rdlowD tF @PHITA 9he spe density of luminous dusty strEforming glxies t z b R X gfeEP nd vefyge imging of ultrred glxies from rershelEeveF9D estrophysil journlFD VQP @IAF pF UVF Further information on publisher's website: Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. ABSTRACT Until recently, only a handful of dusty, star-forming galaxies (DSFGs) were known at z>4, most of them significantly amplified by gravitational lensing. Here, we have increased the number of such DSFGs substantially, selecting galaxies from the uniquely wide 250, 350, and 500 μm Herschel-ATLAS imaging survey on the basis of their extremely red far-infrared colors and faint 350 and 500 μm flux densities, based on which, they are expected to be largely unlensed, luminous, rare, and very distant. The addition of ground-based continuum photometry at longer wavelengths from the James Clerk Maxwell Telescope and the Atacama Pathfinder Experiment allows us to identify the dust peak in their spectral energy distributions (SEDs), with which we can better constrain their redshifts. We select the SED templates that are best able to determine photometric redshifts using a sample of 69 high-redshift, lensed DSFGs, then perform checks to assess the impact of the CMB on our technique, and to quantify the systematic uncertainty associated with our photometric redshifts, σ=0.14 (1 + z), using a sample of 25 galaxies with spectroscopic redshifts, each consistent with our color selection. For Herschel-selected ultrared galaxies with typical colors of S 500 /S 250 ∼2.2 and S 500 /S 350 ∼1.3 and flux densities, S 500 ∼50 mJy, we determine a median redshift, = z 3.66 phot , an interquartile redshift range, 3.30-4.27, with a median rest-frame 8-1000 μm luminosity, L IR , of 1.3× 1013 L e . A third of the galaxies lie at z>4, suggesting a space density, ρ z>4 , of ≈6×10 −7 Mpc −3 . Our sample contains the most luminous known star-forming galaxies, and the most overdense cluster of starbursting proto-ellipticals found to date.