<p>I think the answer to this isn't that Coma-type galaxy clusters are interesting, it's that galaxy clusters are interesting. <a href="https://iopscience.iop.org/article/10.1088/2041-8205/782/1/L3/pdf" rel="nofollow noreferrer">Chiang et al. (2014)</a> talks about the importance of studying protoclusters as a means of understanding how galaxies evolve over time.</p>

<blockquote>
  <p>Galaxy clusters are extreme products of structure formation. They are ideal laboratories to study galaxy assembly, quenching, and sub/super-halo galaxy environments. It has become clear that to obtain a complete picture of cluster formation, we also need to find and study their progenitors at high redshifts that  were  still forming.</p>
</blockquote>

<p>In their paper, they discuss the discovery of a large number of new protoclusters. They bin their protoclusters by mass and designate them as "Fornax-type" (<span class="math-container">$M_{z=0} = 1-3\times 10^{14}\ M_{\odot}$</span>), "Virgo-type" (<span class="math-container">$M_{z=0} = 3-10\times 10^{14}\ M_{\odot}$</span>), or "<strong>Coma-type</strong>" (<span class="math-container">$M_{z=0} &gt; 10^{15}\ M_{\odot}$</span>). Clearly, they're using present-day clusters as analogs to describe what these protoclusters may turn into as they continue to evolve. The fact that a protocluster is considered a Coma-type cluster, is only based on the mass. Astronomer's aren't so much interested in studying Coma-type protoclusters specifically, they're just studying protoclusters and the high mass protoclusters are considered Coma-type protoclusters.</p>

<p>It's very possible that you were preferentially seeing references to Coma-type clusters because Virgo- or Fornax-type clusters are harder to find (being of smaller mass) and so there is an observational bias that preferentially makes Coma-type protoclusters easier to find and subsequently publish about.</p>

CC BY-SA 4.0
2020-04-06T14:28:49.683Z
2020-04-06T14:28:49.683Z
zephyr
<p>When the dynamical mass of a proto-cluster of galaxies is ~(1-2)x10<sup>14</sup> M<sub>solar</sub>, the proto-cluster is expected to evolve into a coma-type cluster.</p>

<p>In almost every paper I read about the confirmation of proto-clusters, the authors of the paper are (almost) always interested in proto-clusters (of galaxies) that will eventually evolve into a Coma-type cluster.</p>

<p>Why are astronomers and astrophysicists so interested in studying those type of structures (Coma-type galaxy clusters)? I mean is it interesting that a proto-cluster will eventually evolve into a Coma-type galaxy cluster? Are these structures rare in the universe? </p>

CC BY-SA 4.0
2020-03-30T22:59:04.830Z
Out of curiosity, would you mind linking to one of these papers?
HDE 226868
<galaxy><galactic-dynamics><galaxy-cluster>
What's so interesting about Coma-type galaxy clusters?
RUNN
# What's so interesting about Coma-type galaxy clusters?

(Asked by: username_0 on 2020-03-30)

When the dynamical mass of a proto-cluster of galaxies is ~(1-2)x1014 Msolar, the proto-cluster is expected to evolve into a coma-type cluster.

In almost every paper I read about the confirmation of proto-clusters, the authors of the paper are (almost) always interested in proto-clusters (of galaxies) that will eventually evolve into a Coma-type cluster.

Why are astronomers and astrophysicists so interested in studying those type of structures (Coma-type galaxy clusters)? I mean is it interesting that a proto-cluster will eventually evolve into a Coma-type galaxy cluster? Are these structures rare in the universe?

**Tags:** galaxy, galactic-dynamics, galaxy-cluster

> **Comments:**
> **username_1**: Out of curiosity, would you mind linking to one of these papers?  

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## 1 answers

### Answer by username_2 on 2020-04-06. Score: 2

I think the answer to this isn't that Coma-type galaxy clusters are interesting, it's that galaxy clusters are interesting. [Chiang et al. (2014)](https://iopscience.iop.org/article/10.1088/2041-8205/782/1/L3/pdf) talks about the importance of studying protoclusters as a means of understanding how galaxies evolve over time.

> Galaxy clusters are extreme products of structure formation. They are ideal laboratories to study galaxy assembly, quenching, and sub/super-halo galaxy environments. It has become clear that to obtain a complete picture of cluster formation, we also need to find and study their progenitors at high redshifts that were still forming.

In their paper, they discuss the discovery of a large number of new protoclusters. They bin their protoclusters by mass and designate them as "Fornax-type" ($M\_{z=0} = 1-3\times 10^{14}\ M\_{\odot}$), "Virgo-type" ($M\_{z=0} = 3-10\times 10^{14}\ M\_{\odot}$), or "**Coma-type**" ($M\_{z=0} > 10^{15}\ M\_{\odot}$). Clearly, they're using present-day clusters as analogs to describe what these protoclusters may turn into as they continue to evolve. The fact that a protocluster is considered a Coma-type cluster, is only based on the mass. Astronomer's aren't so much interested in studying Coma-type protoclusters specifically, they're just studying protoclusters and the high mass protoclusters are considered Coma-type protoclusters.

It's very possible that you were preferentially seeing references to Coma-type clusters because Virgo- or Fornax-type clusters are harder to find (being of smaller mass) and so there is an observational bias that preferentially makes Coma-type protoclusters easier to find and subsequently publish about.


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