Black Holes and Dark Matter

by Daniele Gaggero (Università di Torino)

Tuesday 9 Nov 2021, 15:00 → 16:00 Europe/Rome

Room 131 (Sala Galilei)

Abstract :  The discovery of gravitational wave signals from merger
events of massive binary-black-hole (BBH) systems have prompted a 
renewed debate in the scientific community about the interplay
 between Black Hole phenomenology and Dark Matter searches. 
On the one hand, Black Holes of primordial origin (PBHs) may have 
formed in the early Universe and could constitute a significant 
portion of the elusive dark matter that, according to standard 
cosmology, makes up the majority of the matter content in the 
universe.
On the other hand, peculiar classes of Black Holes can be studied 
as "portals" to Dark Matter detection in the Gravitational Wave 
channel, due to the large density of DM that is expected to be 
present around them.
In the first part of the talk, I will review the most promising 
multi-messenger avenues towards detection of PBHs.
I will first focus on the radio/X-ray band, and present the 
prospects of discovery for both a hypothetical PBH population 
and the guaranteed population of astrophysical isolated black 
holes in our Galaxy, based on the broad-band emission from the 
interstellar gas that is being accreted onto them. 
Then, I will turn my attention to the gravitational wave domain,
and discuss the merger rate of black-hole binaries. I will 
present a detailed evaluation of the expected rate from a 
generic (subdominant) component of PBHs, and analyze the role 
of future observation at high redshift to identify a primordial
 component on top of the rate associated to astrophysical BHs.

In the final part of my talk, I will turn my attention to the
 impact of Dark Matter overdensities around Intermediate-Mass 
Black Holes, and on their impact on the gravitational waveform 
emitted in presence of an Intermediate-Mass-Ratio inspiral. I 
will demonstrate that the dephasing effect induced by the 
presence of the DM is observable in this channel, and the 
properties of the DM overdensity can be measured by the 
upcoming LISA observatory.