The growth of galactic bulges through mergers in LCDM haloes revisited. I. Present-day properties

We use the Millennium I and II cosmological simulations to revisit the impact of mergers in the growth of bulges in central galaxies in the LCDM scenario. We seed galaxies within the growing CDM haloes using semi-empirical relations to assign stellar and gaseous masses, and an analytic treatment to estimate the transfer of stellar mass to the bulge of the remnant after a galaxy merger. We find that this model roughly reproduces the observed correlation between the bulge-to-total (B/T) mass ratio and stellar mass in present-day central galaxies as well as their observed demographics, although low-mass B/T