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Theoretical models for the expected merger rates of intermediate-mass black holes (IMBHs) are vital for planned gravitational-wave detection experiments such as the Laser Interferometer Space Antenna (LISA). Using collisionless $N$-body simulations of dwarf galaxy (DG) mergers, we examine how the orbital decay of IMBHs and the efficiency of IMBH binary formation depend on the central dark matter (DM) density profile of the merging DGs. Specifically, we explore various asymptotic inner slopes $gamma$ of the DGs DM density distribution, ranging from steep cusps ($gamma=1$) to shallower density profiles ($gamma<1$), motivated by well-known baryonic-feedback effects as well as by DM models that differ from cold DM at the scales of DGs. We find that the inner DM slope is crucial for the formation (or lack thereof) of an IMBH binary; only mergers between DGs with cuspy DM profiles ($gamma=1$) are favourable to forming a hard IMBH binary, whereas when $gamma<1$ the IMBHs stall at a separation of 50-100 pc. Consequently, the rate of LISA signals from IMBH coalescence will be determined by the fraction of DGs with a cuspy DM profile. Conversely, the LISA event rates at IMBH mass scales offer in principle a novel way to place constraints on the inner structure of DM halos in DGs and address the core-cusp controversy. We also show that, with spatial resolutions of $sim$0.1 kpc, as often adopted in cosmological simulations, all IMBHs stall, independent of $gamma$. This suggests caution in employing cosmological simulations of galaxy formation to study BH dynamics in DGs.
We study the effects of black hole dark matter on the dynamical evolution of stars in dwarf galaxies. We find that mass segregation leads to a depletion of stars in the center of dwarf galaxies and the appearance of a ring in the projected stellar su
We use cosmological hydrodynamical simulations of the APOSTLE project along with high-quality rotation curve observations to examine the fraction of baryons in {Lambda}CDM haloes that collect into galaxies. This galaxy formation efficiency correlates
Large dark matter overdensities can form around black holes of astrophysical and primordial origin as they form and grow. This dark dress inevitably affects the dynamical evolution of binary systems, and induces a dephasing in the gravitational wavef
Black holes with masses of $rm 10^6-10^9~M_{odot}$ dwell in the centers of most galaxies, but their formation mechanisms are not well known. A subdominant dissipative component of dark matter with similar properties to the ordinary baryons, known as
This paper presents an alternative scenario to explain the observed properties of the Milky Way dwarf Spheroidals (MW dSphs). We show that instead of resulting from large amounts of dark matter (DM), the large velocity dispersions observed along thei