# Question about galaxy formation and black holes.

1. Mar 1, 2012

### fellupahill

In another topic, a member dave13214321323 or whatever his name is :p said that the popular opinion is that in the early universe gas contracted into denser spaces forming galaxies and black holes were consequences of galaxy formation, not the other way around; Black holes at centers of galaxies were not formed by super massive early stars that when burned out and SNed and formed BHs, collected all the matter around it and formed galaxies?.? The first seems completely logically but the problem is so does the latter. I have read the theory conflicting with dave's post in multiple places, but I'm not sure if I have read dave's tho it is entirely possible I have and dont remember.

Can anyone provide a clear answer with PF Approved Sources?

**I have not the knowledge to make speculation as to what is correct on this topic. I am only asking questions, and probably made a mistake or two in my understanding on this topic and every other. Please correct me if I made any errors.

2. Mar 1, 2012

### Drakkith

Staff Emeritus
I've heard both as possibilities, but I don't know if there is a consensus on it at this time.

3. Mar 2, 2012

### zhermes

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.