Star Formation and Stellar Mass Assembly in Dark Matter Halos: From
  Giants to Dwarfs
  The empirical model of Lu et al. 2014 is updated with recent data and used to
study galaxy star formation and assembly histories. At $z > 2$, the predicted
galaxy stellar mass functions are steep, and a significant amount of star
formation is hosted by low-mass haloes that may be missed in current
observations. Most of the stars in cluster centrals formed earlier than
$z\approx 2$ but have been assembled much later. Milky Way mass galaxies have
had on-going star formation without significant mergers since $z\approx 2$, and
are thus free of significant (classic) bulges produced by major mergers. In
massive clusters, stars bound in galaxies and scattered in the halo form a
homogeneous population that is old and with solar metallicity. In contrast, in
Milky Way mass systems the two components form two distinct populations, with
halo stars being older and poorer in metals by a factor of $\approx 3$. Dwarf
galaxies in haloes with $M_{\rm h} < 10^{11}h^{-1}M_{\odot}$ have experienced a
star formation burst accompanied by major mergers at $z > 2$, followed by a
nearly constant star formation rate after $z = 1$. The early burst leaves a
significant old stellar population that is distributed in spheroids.
