Building galaxies by accretion and in-situ star formation

摘要: We examine galaxy formation in a cosmological AMR simulation, which includes two high resolution boxes, one centered on 3 × 10 14 M⊙ cluster, and void. the evolution of 611 massive (M∗ > M⊙) galaxies. find that fraction final stellar mass is accreted from other galaxies between 15 40% increases with mass. The does not depend strongly environment at given mass, but groups cluster environments are older underwent mergers earlier than lower density environments. On average, stars � 2.5 Gyrs older, 0.15 dex more metal poor formed in-situ. Accreted material typically lies outskirts galaxies; average half-light radius 2.6 times larger in-situ stars. This leads to radial gradients age metallicity for galaxies, qualitative agreement observations. Massive grow by rate approximately 2.6%/Gyr −1 . These have median (mass-weighted) ratio less 0.26 ± 0.21, an absolute limit 0.20, M∗ 12 M⊙. suggests major do dominate accretion history All these results agree qualitatively SPH simulations Oser et al. (2010, 2012).