<p><sub>Note: I am not an astrophysicist. If someone with the relevant expertise finds my analysis of the source paper to be invalid, I would appreciate your help with correcting my answer here.</sub></p>
<p>This is a somewhat complicated question to answer. Black holes may precede galaxies in the form of primordial black holes which according to some models arose in the early Universe from quantum fluctuations. Primordial black holes are currently hypothetical. Supermassive black holes (that you find at the center of galaxies) may not come from these, however. There are a few possible ways that supermassive black holes may have formed:</p>
<ul>
<li>Molecular cloud / dwarf galaxies collapsing to form supermassive stars (SMS) which later further collapsed into <a href="https://en.wikipedia.org/wiki/Supermassive_black_hole" rel="nofollow noreferrer">supermassive black holes</a> (SMBH)</li>
<li>Dwarf galaxies forming massive stars which collapse into massive black holes, which later coalesce into SMBHs</li>
<li>Primordial black holes accreting sufficient matter to become massive black holes, which later coalesce into SMBHs</li>
</ul>
<p>Depending on how strictly you define &quot;galaxy&quot; it does seem most likely that the supermassive black holes formed inside early galaxies, but a type of black hole (primordial black holes) may have preceded galaxies.</p>
<p><strong>Source:</strong></p>
<ul>
<li><a href="http://iopscience.iop.org/0004-637X/596/1/34/pdf/0004-637X_596_1_34.pdf" rel="nofollow noreferrer">Formation of the First Supermassive Black Holes - Bromm and Loeb</a></li>
</ul>
<hr />
<p><strong>UPDATE 10/21/2013</strong>:</p>
<p>This just in, recent observations have ruled out the possibility that SMBHs gain mass only through merging with other black holes. For more, see this <a href="http://www.astronomy.com/news/2013/10/gravitational-waves-know-how-black-holes-grow" rel="nofollow noreferrer">Astronomy.com article</a>.</p>

CC BY-SA 4.0
2021-05-11T15:00:25.050Z
As far as I understand, question as to whether or not primordial black holes exist is still very much on the table.
franz_lyre
CC BY-SA 4.0
2021-05-11T16:51:04.297Z
@f_n_lyre you are correct, the existence of primordial black holes is speculative
Daddy Kropotkin
CC BY-SA 4.0
2021-05-11T16:57:41.957Z
@f_n_lyre Edited to reflect the hypothetical nature of primordial black holes
called2voyage
CC BY-SA 4.0
2021-05-16T02:50:25.343Z
I've just asked [How do we know that supermassive black holes can gain mass by means other than merging with other supermassive black holes?](https://astronomy.stackexchange.com/q/43821/7982)
uhoh
CC BY-SA 4.0
2013-10-21T17:59:19.230Z
2021-05-11T16:57:23.040Z
2021-05-11T16:57:23.040Z
called2voyage
<p>In other terms, did galaxies grow around black holes at their center? </p>

<black-hole><galaxy><cosmology><galaxy-center>
Which came first: black holes or galaxies?
Kyriakos Kyritsis
# Which came first: black holes or galaxies?

(Asked by: username_0 on 2013-10-20)

In other terms, did galaxies grow around black holes at their center?

**Tags:** black-hole, galaxy, cosmology, galaxy-center

---

## 1 answers

### Answer by username_1 on 2013-10-21. Score: 8

Note: I am not an astrophysicist. If someone with the relevant expertise finds my analysis of the source paper to be invalid, I would appreciate your help with correcting my answer here.

This is a somewhat complicated question to answer. Black holes may precede galaxies in the form of primordial black holes which according to some models arose in the early Universe from quantum fluctuations. Primordial black holes are currently hypothetical. Supermassive black holes (that you find at the center of galaxies) may not come from these, however. There are a few possible ways that supermassive black holes may have formed:

* Molecular cloud / dwarf galaxies collapsing to form supermassive stars (SMS) which later further collapsed into [supermassive black holes](https://en.wikipedia.org/wiki/Supermassive_black_hole) (SMBH)
* Dwarf galaxies forming massive stars which collapse into massive black holes, which later coalesce into SMBHs
* Primordial black holes accreting sufficient matter to become massive black holes, which later coalesce into SMBHs

Depending on how strictly you define "galaxy" it does seem most likely that the supermassive black holes formed inside early galaxies, but a type of black hole (primordial black holes) may have preceded galaxies.

**Source:**

* [Formation of the First Supermassive Black Holes - Bromm and Loeb](http://iopscience.iop.org/0004-637X/596/1/34/pdf/0004-637X_596_1_34.pdf)

---

**UPDATE 10/21/2013**:

This just in, recent observations have ruled out the possibility that SMBHs gain mass only through merging with other black holes. For more, see this [Astronomy.com article](http://www.astronomy.com/news/2013/10/gravitational-waves-know-how-black-holes-grow).

> **Comments:**
> **username_2**: As far as I understand, question as to whether or not primordial black holes exist is still very much on the table.  
> **username_3**: @f_n_lyre you are correct, the existence of primordial black holes is speculative  
> **username_1**: @f_n_lyre Edited to reflect the hypothetical nature of primordial black holes  
> **username_4**: I've just asked [How do we know that supermassive black holes can gain mass by means other than merging with other supermassive black holes?](https://astronomy.stackexchange.com/q/43821/7982)  

---

