#  Black Hole Initiative Colloquium 

 



####  calendar\_today Date and Time 

 **March 31, 2020** 

 01:30PM - 02:30PM EDT 

####  pin\_drop Location 

 **Zoom - Please see link below**  



 

 



 

 [Zoom Link](https://harvard.zoom.us/j/405994301)

 **Davide Gerosa (University of Birmingham)**

 **Title: Growing up. The next generation of black holes moves out of the cluster.**

 **Abstract:** Pair instabilities in supernovae might prevent the formation of black holes with masses between ∼50 and ∼130 solar masses. Multiple generations of black-hole mergers provide a possible way to populate this "mass gap" from below. However, this requires an astrophysical environment with a sufficiently large escape speed to retain merger remnants and prevent them from being ejected by gravitational-wave recoils. We show that a single LIGO/Virgo observation of a black hole in the pair-instability mass gap implies that its progenitors grew in an environment with escape speed >50 km/s. This is larger than the escape speeds of most globular clusters, requiring denser and heavier environments such as nuclear star clusters or disks-assisted migration in galactic nuclei. A single detection in the mass gap would also hint at the existence of a much larger population of first-generation events from the same environment, thus providing a tool to disentangle the contribution of different formation channels to the observed merger rate.



 

 



 

 

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