Simulations of galaxy formation and evolution

Abstract

We discuss recent results of hydrodynamical simulations of galaxy formation in a Λ Cold Dark Matter universe, focusing on galaxies of similar mass to the Milky Way, and with a variety of formation and merger histories. We investigate the present-day properties of disks and spheroids, in terms of stellar ages, spatial structure and dynamics; as well as the evolution of the disks. We find that disks are young, and usually composed of two or more components: the youngest stars define thinner disks that rotate ∼2 times faster than thicker disks. The latter are populated by older stars, and have 2-3 times larger velocity dispersions than the younger population. Spheroids are old and are very diverse; their inner regions are sometimes characterized by the presence of prominent bars. The disks evolve significantly during evolution. In particular, we find that major mergers and misaligned gas accretion are able to completely or partially destroy disks. These results suggest that the survival probability of disks, and therefore the final morphology of galaxies, strongly depends on the particular formation and merger history of their parent haloes. Our results show that galaxy diversity arises naturally in ΛCDM as a result of the different evolutionary paths of dark matter haloes. We also discuss the most important open problems in this field.

The Star Formation Histories of Disk Galaxies: The Live, the Dead, and the Undead

“…Models with inadequate feedback inevitably turn too much of the initial baryons into stars, resulting in galaxies which form too fast, are too massive, and are too centrally concentrated. Getting the feedback right has been a difficult task, one that is not yet complete (see Scannapieco 2012, andElahi et al 2016, for comparisons of various recent attempts). This difficulty is usually attributed to the inevitably incomplete resolution of small-scale astrophysical processes-such as the interaction of stellar winds and radiation with the very inhomogeneous interstellar medium-which are central to the feedback processes.…”