The cosmological formation of massive galaxies

In a hierarchically organised universe massive galaxies are built up from stars
that are formed from gas close to the center of the galaxy (in-situ) and from
accreted stellar matter formed in external galaxies (ex-situ). From analysing a
sample of high-resolution cosmological simulations of the formation of
individual massive galaxies, we find these two phases of star formation to be a
useful distinction in understanding the rapid size evolution of elliptical
galaxies and the origin of their fundamental scaling relations.