Inside-out Infall Formation of Disk Galaxies: Do Predictions Differ from Models without Size Evolution?

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Abstract
We develop an idealized inside-out formation model for disk galaxies to include a realistic mix of galaxy types and luminosities that provides a fair match to the traditional observables. The predictions of our infall models are compared against identical models with no-size evolution by generating fully realistic simulations of the Hubble Deep Field, from which we recover the angular size distributions. We find that our infall models produce angular size distributions that are nearly identical to those of our no-size evolution models in the case of a Ω=0 geometry but produce slightly smaller sizes in the case of a Ω=1 geometry, a difference we associate with the different amounts of cosmic time in our two models for evolving to relatively low redshifts (z ≈ 1-2). Our infall models also predict a slightly smaller (11%-29%) number of large (disk scale lengths greater than 4 h50−1 kpc) galaxies at z ≈ 0.7 for the Canada France Redshift Survey, as well as different increases in the central surface brightness of the disks for early-type spirals, the infall model predicting an increase by 1.2 mag out to z ≈ 2(Ω=0) and z ≈ 1(Ω=1), while our no-size evolution models predict an increase of only 0.5 mag. This result suggests that infall models could be important for explaining the 1.2-1.6 mag increase in surface brightness reported by Schade and coworkers.
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