A warm mode of gas accretion on forming galaxies

Understanding galaxy's formation is one of the most challenging and di?cult topics in modern cosmology. While the concept of galaxies as island universe can be traced back to Wright (1750) and Kant (1755) the study of the formation of galaxies is still a hot and discuss issue, even if its theoretical background lies now in the so-called Standard Cosmo- logical model. According to this model, our universe is composed by Dark Energy(73%), Dark Matter (23%) and baryonic matter (4%). Once the cosmological parameters are ?xed, is it possible to investigate the formation of the structures in the universe. Basical- ly the structure growth is driven (almost) entirely by gravity: the evolution of primordial uctuation in the density ?eld can be model through a simple treatment, describing the universe as a newtonian uid in expansion. The ?nal results is a structure of DM halos connected by walls and ?lamens: the large-scale structure of the universe. The galaxies form when the baryon gas cools and condenses in the potential wells of dark matter halos. The rather stringent constraints on cosmological parameters now allows us to precisely set the initial conditions from which the formation of cosmic structures has started. As a consequence, understanding the complex astrophysical processes related to the evolution of the baryonic component represents now the missing link towards a successful description of galaxy formation and evolution.