Matteo Della Rocca "Probing black hole environments with ringdown"

Friday 21 Nov 2025, 12:30 → 14:30 Europe/Rome

Sala Lauree (Marconi building)

Black holes are rarely isolated: they are often embedded in dense astrophysical environments which can leave a significant imprint on gravitational waves emitted during dynamical processes. The ringdown, i.e. the last stage of a binary coalescence, is particularly sensitive to beyond-vacuum General Relativity signatures and therefore provides a promising probe of environmental effects. In this talk, I will discuss the observability of such effects with current and future experiments, showing that only sufficiently compact environments produce detectable modifications in the ringdown signal. In particular, I will focus on two examples: anisotropic fluid halos and gravitational atoms (black holes surrounded by clouds of massive scalar fields that can mimic dark matter halos). While the former are generally too diffuse to yield observable signatures, I will show that scalar clouds can induce a shift on the ringdown spectrum that could be, in principle, observed even with current detectors.