FTR, if you wondered what they meant by "annihilation signals from the dark matter microhalo", apparently one of the theories for what makes up dark matter is WIMPs which are special particles that interact weakly with normal particles but can interact with each other and result in creation of other, better observable particles.

The theory is that in the early universe, WIMPs were created spontaneously due to massive temperatures of the primordial plasma, but later as the universe expanded and cooled, this creation didn't work. However, the WIMPs would still be able to react with each other, reducing their numbers, until they'd be so rare that annihilations are such a rare event that they don't significantly reduce their numbers any more. Then space expanded even further.

https://arxiv.org/pdf/1403.4495.pdf

Apparently due to the strong perturbances of the dark matter that this black hole creates, it creates potentially detectable annihilations, and they discuss which scenarios can be excluded or detected with data generated by the FERMI-LAT gamma ray telescope.

Not a physicist though, so please correct me if I'm wrong.