<p>I'm going to say, &quot;probably not&quot;, because (as tfb points out) we have very good evidence for SMBHs in other galaxies -- in particular galaxies with <em>active nuclei</em> where the phenomenon associated with accretion disks around BHs are seen. The most extreme case is probably NGC 4395, where a Seyfert 1 nucleus and associated radio jets exist. The best estimates for accretion-disk+SMBH models suggest a SMBH mass of only a few hundred thousand solar masses; a recent direct dynamical measurement (<a href="https://ui.adsabs.harvard.edu/abs/2015ApJ...809..101D" rel="nofollow noreferrer">den Brok et al. 2015</a>) indicate a central &quot;dark object&quot; gravitational mass of <span class="math-container">$M_{\rm BH} \sim 400,000$</span> solar masses. There are numerous other galaxies with active nuclei where the estimated or measured central-object masses are <span class="math-container">$M_{\rm BH} \sim 10^{6}$</span>--<span class="math-container">$10^{7} M_{\odot}$</span>.</p>
<p>This is rather difficult to square with the claim that &quot;above a critical mass, a dark matter clump could gravitationally collapse into a supermassive black hole&quot; because if you follow up the associated reference to <a href="https://ui.adsabs.harvard.edu/abs/2021MNRAS.502.4227A/abstract" rel="nofollow noreferrer">Argüelles et al. (2021)</a>, it ends up predicting a critical mass of <span class="math-container">$\sim 10^{8} M_{\odot}$</span>. This is consistent with something like M87 (<span class="math-container">$M_{\rm BH} \sim 6 \times 10^{9} M_{\odot}$</span>), but not with all the evidence for accreting SMBHs in galaxy centers with <span class="math-container">$M_{\rm BH} &lt; 10^{7} M_{\odot}$</span>.</p>
<p>The &quot;flares observed from Sgr A* in recent years&quot; are, I believe, generally supposed to be evidence for a very weak, transient accretion disk around the SMBH (e.g., <a href="https://www.mpe.mpg.de/6591435/Flares-from-the-black-hole" rel="nofollow noreferrer">the discussion on this web page</a>), and so would be difficult to explain with this model.</p>

CC BY-SA 4.0
2021-05-23T13:36:38.647Z
2021-05-23T13:36:38.647Z
Peter Erwin
<p>A recent <a href="https://arxiv.org/abs/2105.06301" rel="nofollow noreferrer">paper</a> (related <a href="https://www.sciencealert.com/wild-new-paper-proposes-the-center-of-the-milky-way-might-not-be-a-black-hole" rel="nofollow noreferrer">news</a>) shows that Sgr A* at the center of the Milky Way galaxy could be a dark matter core, instead of a supermassive black hole, according to their calculation using the astrometry data of the 17 best-resolved S-stars and the mysterious G2. The dark matter particles could be 56 keV fermions, which they call &quot;darkinos&quot;.</p>
<p>The team also proposes that, above a critical mass, a dark matter clump could gravitationally collapse into a supermassive black hole, like the one in M87.</p>
<p>Is this dark matter model possible? Do the flares from Sgr A* observed in recent years support or contradict this model? Can LHC or other smaller particle colliders or detectors on Earth help to confirm or rule out the particle?</p>

CC BY-SA 4.0
2021-05-21T17:52:06.880Z
@tfb The team also proposes that, above a critical mass, a dark matter clump could gravitationally collapse into a supermassive black hole. I have edited my question to reflect this.
NeutronCat
<supermassive-black-hole><dark-matter><particles>
Could Sgr A* be a core of dark matter instead of a supermassive black hole?
NeutronCat
# Could Sgr A* be a core of dark matter instead of a supermassive black hole?

(Asked by: username_0 on 2021-05-21)

A recent [paper](https://arxiv.org/abs/2105.06301) (related [news](https://www.sciencealert.com/wild-new-paper-proposes-the-center-of-the-milky-way-might-not-be-a-black-hole)) shows that Sgr A\* at the center of the Milky Way galaxy could be a dark matter core, instead of a supermassive black hole, according to their calculation using the astrometry data of the 17 best-resolved S-stars and the mysterious G2. The dark matter particles could be 56 keV fermions, which they call "darkinos".

The team also proposes that, above a critical mass, a dark matter clump could gravitationally collapse into a supermassive black hole, like the one in M87.

Is this dark matter model possible? Do the flares from Sgr A\* observed in recent years support or contradict this model? Can LHC or other smaller particle colliders or detectors on Earth help to confirm or rule out the particle?

**Tags:** supermassive-black-hole, dark-matter, particles
> **Comments:**
> **username_0**: @tfb The team also proposes that, above a critical mass, a dark matter clump could gravitationally collapse into a supermassive black hole. I have edited my question to reflect this.  

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## 1 answers

### Answer by username_1 on 2021-05-23. Score: 4

I'm going to say, "probably not", because (as tfb points out) we have very good evidence for SMBHs in other galaxies -- in particular galaxies with *active nuclei* where the phenomenon associated with accretion disks around BHs are seen. The most extreme case is probably NGC 4395, where a Seyfert 1 nucleus and associated radio jets exist. The best estimates for accretion-disk+SMBH models suggest a SMBH mass of only a few hundred thousand solar masses; a recent direct dynamical measurement ([den Brok et al. 2015](https://ui.adsabs.harvard.edu/abs/2015ApJ...809..101D)) indicate a central "dark object" gravitational mass of $M\_{\rm BH} \sim 400,000$ solar masses. There are numerous other galaxies with active nuclei where the estimated or measured central-object masses are $M\_{\rm BH} \sim 10^{6}$--$10^{7} M\_{\odot}$.

This is rather difficult to square with the claim that "above a critical mass, a dark matter clump could gravitationally collapse into a supermassive black hole" because if you follow up the associated reference to [Argüelles et al. (2021)](https://ui.adsabs.harvard.edu/abs/2021MNRAS.502.4227A/abstract), it ends up predicting a critical mass of $\sim 10^{8} M\_{\odot}$. This is consistent with something like M87 ($M\_{\rm BH} \sim 6 \times 10^{9} M\_{\odot}$), but not with all the evidence for accreting SMBHs in galaxy centers with $M\_{\rm BH} < 10^{7} M\_{\odot}$.

The "flares observed from Sgr A\* in recent years" are, I believe, generally supposed to be evidence for a very weak, transient accretion disk around the SMBH (e.g., [the discussion on this web page](https://www.mpe.mpg.de/6591435/Flares-from-the-black-hole)), and so would be difficult to explain with this model.


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