On the size evolution of early type galaxies

GIAN LUIGI GRANATO; CINTHIA RAGONE-FIGUEROA; MARIO G. ABADI

Buenos Aires

Workshop; Second Workshop on Numerical and Observational Astrophysics: From the First Structures to the Universe Today; 2011

IAFE

We present numerical simulations of the effect of baryonic mass loss on the structure of a spheroidal stellar system, embedded in a dark matter halo. This process, invoked as a possible explanation of the observed size increase of early-type galaxies since z ? 2, could be caused either by quasi-stellar objects/starburst driven galactic winds, promptly ejecting from early-type galaxies the residual gas and halting star formation (galactic winds), or by stellar mass returned to the interstellar medium (ISM) in the final stages of stellar evolution. Indeed, we find that a conceivable loss of ? 50% of the baryonic mass can produce a significant size increase. However, the puffing up due to galactic winds occurs when the stellar populations are much younger than the estimated ages > 0.5 Gyr of compact high-z early-type galaxies. Therefore, while it may have had a role in deciding the final structure of early-type galaxies, it cannot explain the evolution observed so far of their size-mass relation. Conversely, the mass loss due to stellar evolution could cause a modest expansion of passively evolving stellar systems, contributing to, without dominating, the observed evolution of their mass-size relationship.