Galaxy Formation & Evolution
In the current cosmological paradigm, early fluctuations of the dark matter distribution grow into stable structures (halos), attracting baryonic matter that cools, triggering star formation. Halos merge to form larger galaxies, which develop a spheroidal, stellar component and inflowing cooling gas or dark matter collapse to spawn a central, massive black hole. The relationship between the mass of the black hole and that of the surrounding spheroid can be explained if the black hole regulates the star formation via some feedback mechanism. The ‘baryon physics’ comprising gas collapse, star and black hole formation and subsequent feedback, is the main bottleneck in our understanding of galaxy formation.