Institute for Advanced Study Informal Astrophysics Seminar - SPECIAL TIME

The popular model for the formation of early-type galaxies is the hierarchical merging scenario. However, the details and frequency of merging are not yet known, particularly in dense environments. The high-mass end of the galaxy luminosity function, as the extreme example of the merger phenomenon, is the most sensitive to various merger model assumptions and thus provides an ideal testing ground for these models. I will present recent work utilizing wide-area spectroscopic surveys to place constraints on the star formation and merger histories of the most massive galaxies in the universe since z~1. In particular, I will show that massive red-sequence galaxies have had very little star formation since z~1, thus limiting the importance of gas-rich mergers since that epoch, and show that the number density of very massive galaxies has evolved little in that same epoch, suggesting that very massive galaxies assembled their stellar mass at z>1. I will close with a brief introduction of PRIMUS, a new spectoscopic survey aimed at observing 15 square degrees of the southern sky with high-quality archival optical, infrared, and X-ray data and obtaining 300,000 galaxy redshifts to z~1. PRIMUS will be the largest intermediate-redshift galaxy survey to date as well as the largest sample of Spitzer-detected objects and will allow for a broad-range of investigations.