Publication : t23/126

Abstract:
The absence of direct observations of cold dark matter particles calls for a better understanding of alternative scenarios. In particular, scenarios involving ultralight bosons with a mass below 1 eV have experienced a resurgence of interest in recent years. They preserve the successes of the standard cold dark matter model at large scales but alter the dynamics at galactic scales. Including self-interactions to such scenarios endows dark matter with fluid-like behavior with non-negligible effective pressure, distinguishing it from the conventional ultralight dark matter. We investigated the accretion and dynamicalfriction applied on a black hole moving in a dark matter cloud, both in subsonic and supersonic regimes. Our findings reveal that while the subsonic regime primarily involves accretion, the supersonic regime introduces additional dynamical friction characterized by a term similar to the one obtained by Chandrasekhar for collisionless particles. Nonetheless, in both regimes, the magnitude of the accretion force and dynamical friction remains lower than that observed for cold or collisionless ultralight dark matter. In this framework, we analyzed the effects of these forces on the gravitational-wave signals emitted by binary black holes inside a self-interacting scalar field dark matter cloud. To a fist approximation, correction terms at -4PN and -5.5PN orders appear, exerting an influence on the phase of the gravitational-wave signal. Prospective observations by LISA and B-DECIGO have the potential to detect these effects across a broad spectrum of scalar masses and self-interaction couplings. Our analysis demonstrates that the instances in which the detection of these effects is most probable are Extreme Mass Ratio Inspirals (EMRIs) observed by LISA. Presently, this approach stands as the sole means to constrain self-interacting scalar dark matter with clouds smaller than 0.1 pc.

125032_BOUDON_2023_archivage.pdf