报告题目: Universality and peculiarity in galaxy formation
报告人: Dr. David Elbaz (CEA-Saclay, France)
报告摘要:An ever-increasing amount of information converge towards a picture or galaxy formation where galaxies evolve through a rather secular star formation history as opposed to rapidly and strongly varying. But what causes this universality among galaxies with very different morphologies and social lives? Often considered negligible, on the basis of its classical perception, the environment appears to play a key role in regulating the growth of galaxies and its fluctuations with cosmic time. Numerical simulations now converge, when pushed to scales smaller than 5 pc, and provide a physical explanation why gas-rich galaxies major mergers rarely exhibit strong starburst signatures. When looked at carefully with the resolving power of ALMA, galaxies start revealing some subtle effects of mergers consistent with those hydrodynamic simulations. Starbursts hidden in the so-called star formation main sequence of galaxies show up that may play a key role in understanding the morphological transformation of disks into spheroids. However, a major tension hides behind this idyllic picture: cosmological models fail to reproduce the observed evolution of individual galaxies and extensively use sub-grid recipes for feedback with intensities difficult to reconcile with the observed universality. A major question emerges from these considerations: is there something fundamentally wrong with our theoretical assumptions on how galaxies formed, and consequently on e.g. the behaviour/nature of dark matter, or is this only reflecting the complexity of the behaviour of baryons?