# Question about galaxy formation and black holes.

by fellupahill
Tags: black, formation, galaxy, holes
 P: 1,261 The standard model of structure formation is called "$\Lambda$CDM" or "Lambda Cold Dark Matter", where 'lambda' refers to the cosmological constant---or 'dark energy'. According to this model, initial over-density of dark matter (DM) grew into massive 'halos' of DM, which then accreted significant amounts of gas to for galaxies. Most of the earliest star formation is expected to have started once gas was being funneled into those protogalaxies---I'm not sure how much could happen outside-of (or before) those proto-galaxies started to form. So the paradigm is dark matter halos ---> galaxies from gas accretion. The role of super-massive black-holes (SMBHs) is more unclear. It isn't known how exactly SMBHs are able to form---thats a big issue in-and-of itself. The general picture is that they form from giant ("Population III") stars, in the earliest stages of star formation. This suggests the BH's started to form after the proto-galaxies began to form. Further-more, for the initial, smaller, BH's to grow into SMBH's they need LOTS of ambient gas accretion---which requires a dense galactic environment; again suggesting that some type of proto-galaxy was already in place. As Drakkith said, this is far from a resolved issue---and the details are lacking; its a very active field of research in galaxy formation.