Star Formation and Merging in Massive Galaxies at z < 2
Abstract
Observing massive galaxies at various redshifts is one of the most straightforward and direct approaches towards understanding galaxy formation. There is now largely a consensus that the massive galaxy (M* > 1011 M0) population is fully formed by z~1, based on mass and luminosity functions. However, we argue that the latest data can only rule out number and mass density evolution of a factor of > 2-3 at z < 1.5. We furthermore show that the star formation history of M* > 1011 M0 galaxies reveals that 40+/-5% of galaxies with M* > 1011 M0 at z~1 are undergoing star formation that effectively doubles their stellar mass between z = 0.4 - 1.4. These massive galaxies also undergo 0.9+0.7-0.5 major mergers during this same time period.
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