Galaxy mass assembly
With Francoise Combes and Benoit Semelin, we have used multi-zoom simulations to investigate the way galaxies assemble their baryonic mass. We ran a series of N-body only and N=body + hydrodynamics simulations, zooming on a dense region (15 times the mean density of the Universe at z=0.46). I studied the mass assembly of galaxies, namely, how they assemble their baryonic mass, discriminating between the mass asseembled by mergers and by smooth accretion. To do this, I detected the dark matter and baryonic structures using a modified version of AdaptaHOP (Aubert et al 2004, Tweed et al. 2009), and buit merger trees. I found a mean accretion fraction of 77%, with low mass galaxies assembling their mass mostly from accretion. I also found some evidence for downsizing in these simulations: massive galaxies have have an old stellar populations, whereas low-mass galaxies form stars at every epoch.
I am currently comparing the statistical (mass function) and internal (concentration, spin) properties of haloes between the DM only and the hydrodynamic simulations, to understand how the baryonic physics shapes the haloes.