Astronomy Tea Talk

Massive galaxies in the nearby universe typically have very little cold gas, they host old stellar populations and exhibit extremely low specific star formation rates. Therefore, studies of these galaxies typically find that essentially all of the stellar mass growth takes place through mergers and other gravitational interactions, with the relative importance of each process still debatable. For example, while some authors find that major dry mergers contribute significantly to the mass evolution of massive galaxies, others find only a mild contribution or none at all. Other studies argue that minor mergers and low mass accretion events contribute at least some of the stellar mass growth in massive galaxies over a longer timescale. In this talk I will present results from multiple studies of the contribution of minor mergers to the mass growth of massive galaxies at z<0.7. I will show that essentially all nearby ellipticals have morphological disturbances in their stellar bodies that can be associated with minor merger activity. In addition, I will discuss a purely statistical study of the satellite galaxies around luminous red galaxies in SDSS and show that major mergers are an unlikely contributor to their mass growth. Lastly, I will show that the colors of massive galaxy at extreme radii are consistent with the minor merger growth model.