The structural and photometric properties of early-type galaxies in hierarchical models
Abstract
We present predictions for the structural and photometric properties of early-type galaxies in the cold dark matter cosmology (LambdaCDM). We use the GALFORM code, which tracks the evolution of the disk and bulge components of a galaxy, using a self-consistent model to compute the scalelengths. The sizes of galactic disks are determined by the conservation of the angular momentum of cooling gas. The sizes of merger remnants are computed by applying the virial theorem and conserving the binding energy of the progenitors and their orbital energy. We compare the model predictions with observational results derived from the SDSS. The model enjoys a number of notable successes, such as reproducing the local Faber-Jackson relation (velocity dispersion-luminosity), the velocity dispersion-age relation, and the fundamental plane relating the luminosity, velocity dispersion and effective radius of spheroids. We study how the residuals around the zero-point of the fundamental plane depend on galaxy properties. However, there are some important disagreements between the model predictions and observations: the brightest model spheroids have effective radii smaller than observed and the zero-point of the fundamental plane shows little or no evolution with redshift in the model. We examine in detail the physical ingredients of our calculation of galaxy sizes, showing which components have the most influence on our results.Keywords
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