<p>As Pela said in the comment, it is highly redshift dependent so there is no straight answer. "Some" is the safest option.</p>

CC BY-SA 4.0
2019-12-12T19:48:02.253Z
2019-12-12T19:48:02.253Z
Sean Mooney
<p>I've been saying "some". I can't find a reference for a particular percentage.</p>

<p>This seems to address the question to some extent; <a href="https://arxiv.org/abs/astro-ph/0108389" rel="nofollow noreferrer">https://arxiv.org/abs/astro-ph/0108389</a> would "roughly 1%" be in the right ballpark for an answer then?</p>

<p>pesa points out this is redshift-dependent. I am looking for a ballpark figure of the fraction of AGN at <span class="math-container">$z &lt; 1$</span>.</p>

CC BY-SA 4.0
2019-12-09T12:45:57.687Z
don't let my hat scare you, it's "hat season" here. I added some minimal research to your question; "I looked and didn't find anything" is not a good way to elicit good quality answers, it's better to add at least a little evidence of research to a question. *Welcome to Stack Exchange!*
uhoh
CC BY-SA 4.0
2019-12-09T14:10:37.080Z
Hi Sean, the answer to your question is highly redshift-dependent. AGN activity peaked around z ~ 2, while earlier and later epochs have significantly smaller fractions. If you mean "today" (i.e. z = 0), you should probably add that information to your question.
pela
CC BY-SA 4.0
2019-12-09T14:16:35.113Z
That's true. The number I'm probably after is AGN fraction integrated from z = 0 to z = ~0.7.
Sean Mooney
CC BY-SA 4.0
2020-01-12T12:30:58.217Z
Note that the paper you link to is about the fraction of z ~ 0 galaxies with "Seyfert 1" nuclei, which are not the only type of AGN. So that should be considered a lower limit.
Peter Erwin
CC BY-SA 4.0
2020-01-12T12:46:04.317Z
In addition to the redshift dependence, there is also a strong dependence on stellar mass (more massive galaxies are more likely to host AGN).
Peter Erwin
<active-galaxy>
What fraction of galaxies host active galactic nuclei?
Sean Mooney
# What fraction of galaxies host active galactic nuclei?

(Asked by: username_0 on 2019-12-09)

I've been saying "some". I can't find a reference for a particular percentage.

This seems to address the question to some extent; <https://arxiv.org/abs/astro-ph/0108389> would "roughly 1%" be in the right ballpark for an answer then?

pesa points out this is redshift-dependent. I am looking for a ballpark figure of the fraction of AGN at $z < 1$.

**Tags:** active-galaxy
> **Comments:**
> **username_1**: don't let my hat scare you, it's "hat season" here. I added some minimal research to your question; "I looked and didn't find anything" is not a good way to elicit good quality answers, it's better to add at least a little evidence of research to a question. *Welcome to Stack Exchange!*  
> **username_2**: Hi Sean, the answer to your question is highly redshift-dependent. AGN activity peaked around z ~ 2, while earlier and later epochs have significantly smaller fractions. If you mean "today" (i.e. z = 0), you should probably add that information to your question.  
> **username_0**: That's true. The number I'm probably after is AGN fraction integrated from z = 0 to z = ~0.7.  
> **username_3**: Note that the paper you link to is about the fraction of z ~ 0 galaxies with "Seyfert 1" nuclei, which are not the only type of AGN. So that should be considered a lower limit.  
> **username_3**: In addition to the redshift dependence, there is also a strong dependence on stellar mass (more massive galaxies are more likely to host AGN).  

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## 1 answers

### Answer by username_0 on 2019-12-12. Score: 1

As Pela said in the comment, it is highly redshift dependent so there is no straight answer. "Some" is the safest option.


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