Over-population of Black Holes

[wolram]

I find this article hard to believe can there be so many Black Holes in one galaxy, if there are, why are there not many mergers recorded by Ligo.

https://www.sciencedaily.com/releases/2016/09/160907215155.htm

Computer simulations of a spherical collection of stars known as 'NGC 6101' reveal that it contains hundreds of black holes, until now thought impossible. Recent observations already found black hole candidates in similar systems, with this research enabling astrophysicists to map black holes in other clusters. These systems could be the cradle of gravitational wave emission, 'ripples' in the fabric of space-time

 

[mfb]

Hundreds of black holes can still mean one merger per 100 billion years or something like that - unless they form in a binary system, mergers are extremely rare. Those black holes have a few times the mass of sun each, so LIGO won't have such a large detection range for them.

 

[Vanadium 50]

Why don't we see the sky alight with stellar collisions? After all, the styar density is much larger than the black hole density?

 

[mfb]

Well, which fraction of stellar collisions 100 million light years away do we detect?

 

[Chronos]

I'm curious about the apparent lack of consideration for DM in NGC6101. I suspect a massive DM component could also suppress mass segregation. The arxiv version of the subject paper is: http://arxiv.org/abs/1609.01720, A stellar-mass black hole population in the globular cluster NGC 6101?.
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