The infrared side of galaxy formation. I. The local universe in the semi-analytical framework
Abstract
We present a new evolutionary model for predicting the far-UV to sub-mm properties of the galaxy population. This combines a semi-analytic galaxy formation model based on hierarchical clustering (Cole et al 1999) with a spectro-photometric code which includes stellar population evolution and dust reprocessing (Silva et al 1998). The galaxy formation model provides the star formation and metal enrichment histories, together with the gas mass and various geometrical parameters, for a representative sample of galaxies formed in different density environments. These quantities, together with a few other assumptions concerning the spatial distribution of dust and its optical properties, allow us to model the spectral energy distributions of galaxies, taking into account stellar emission and also dust extinction and re-emission. We test our models against the observed spectro-photometric properties of galaxies in the local Universe. They reproduce fairly well the SEDs of normal spirals and starbursts from the far-UV to the sub-mm, and their internal extinction properties. The starbursts follow the observed relationship between the FIR to UV luminosity ratio and the slope of the UV continuum. They also reproduce the observed starburst attenuation law (Calzetti 1999). This result is remarkable, because we use a dust mixture which reproduces the Milky Way extinction law. It suggests that the observed attenuation law is closely related to the geometry of the stars and dust. We compute galaxy luminosity functions over a wide range of wavelengths, which turn out to be in good agreement with observational data in the UV (2000\AA), in the B and K bands, and in the IR ($12-100\mum$)....Keywords
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