Galaxy evolution in the infrared: comparison of a hierarchical galaxy formation model with Spitzer data (original) (raw)

We construct rest-frame luminosity functions (LFs) at 3.6, 4.5, 5.8, 8 and 24 ��m over the redshift range 0< z< 2 for galaxies and 0< z< 4 for optical quasi-stellar objects (QSOs), using optical and infrared (IR) data from the Spitzer Wide-area Infrared Extragalactic (SWIRE) Survey. The 3.6-and 4.5-��m galaxy LFs show evidence for moderate positive luminosity evolution up to z��� 1.5, consistent with the passive ageing of evolved stellar populations. Their comoving luminosity density was found to evolve passively, gradually ...

Abstract: We use a model for the evolution of galaxies in the far-IR based on the LambdaCDM cosmology to make detailed predictions for upcoming cosmological surveys with the Herschel Space Observatory. We use the combined GALFORM semi-analytical galaxy formation model and GRASIL spectrophotometric code to compute galaxy SEDs including the reprocessing of radiation by dust. The model, which is the same as that in Baugh et al.(2005), assumes two different IMFs: a normal solar neighbourhood IMF for ...

Abstract: We make a detailed investigation of the properties of Lyman-break galaxies (LBGs) in the LambdaCDM model. We present predictions for two published variants of the GALFORM semi-analytical model: the Baugh et al.(2005) model, which has star formation at high redshifts dominated by merger-driven starbursts with a top-heavy IMF, and the Bower et al.(2006) model, which has AGN feedback and a standard Solar neighbourhood IMF throughout. We show predictions for the evolution of the rest-frame far-UV luminosity ...

We derive photometric redshifts from 17-band optical to mid-infrared photometry of 78 robust radio, 24-�� m and Spitzer IRAC counterparts to 72 of the 126 submillimetre galaxies (SMGs) selected at 870 �� m by LABOCA observations in the Extended Chandra Deep Field-South (ECDF-S). We test the photometric redshifts of the SMGs against the extensive archival spectroscopy in the ECDF-S. The median photometric redshift of identified SMGs is z= 2.2��0.1, the standard deviation is �� z= 0.9 and we identify 11 (��� 15 ...

We use the combined GALFORM semi-analytical model of galaxy formation and GRASIL spectrophotometric code to investigate the properties of galaxies selected via their submillimetre (submm) emission. The fiducial model we use has previously been shown to fit the properties of local Ultra-Luminous Infrared Galaxies, as well as the number counts of faint submm galaxies. Here, we test the model in more detail by comparing the SEDs and stellar, dynamical, gas and halo masses of submm galaxies against observational data. We precisely mimic the submm and radio selection function of the observations and show that the predicted far-infrared properties of model galaxies with S850 > 5mJy and S1.4 > 30μJy are in good agreement with observations. Although the dust emission model does not assume a single dust temperature, the far-infrared SEDs are well described by single component modified blackbody spectrum with characteristic temperature 32 +/- 5K, in good agreement with observations. We also find evidence that the observations may have uncovered evolution in the far-infrared-radio relation in ULIRGs out to z ~ 2. We show that the predicted redshift distribution of submm galaxies provides a reasonable fit to the observational data with a median redshift z = 2.0. The radio-selected subset of submm galaxies are predicted to make up approximately 75 per cent of the population and peak at z = 1.7, in a reasonable agreement with the observed radio detected fraction and redshift distribution. However, the predicted K band and mid-infrared (3-8μm) flux densities of the submm galaxies [and Lyman-Break Galaxies (LBGs)] are up to a factor of 10× fainter than observed. We show that including the stellar thermally pulsating asymptotic giant branch phase in the stellar population models does not make up for this deficit. This discrepancy may indicate that the stellar masses of the submm galaxies in the model are too low: M* ~ 1010Msolar, while observations suggest more massive systems, M* >~ 1011Msolar. However, if the predicted K- and 3-8-μm extinctions in the model could be dramatically reduced, then this would reduce, but not eliminate, this discrepancy. Finally, we discuss the potential modifications to the models which may improve the fit to the observational data, as well as the new observational tests which will be made possible with the arrival of new facilities, such as Submillimetre Common-User Bolometer Array2.

Abstract: We present new results from a multi-wavelength model of galaxy formation, which combines a semi-analytical treatment of the formation of galaxies within the CDM framework with a sophisticated treatment of absorption and emission of radiation by dust. We find that the model, which incorporates a top-heavy IMF in bursts, agrees well with the evolution of the rest-frame far-UV luminosity function over the range z= 0-6, with the IR number counts in all bands measured by SPITZER, and with the observed evolution of the mid-IR luminosity ...