Cusp-to-core transition in low-mass dwarf galaxies induced by dynamical heating of cold dark matter by primordial black holes

TL;DR

This study uses high-resolution N-body simulations to show that primordial black holes can induce a cusp-to-core transition in low-mass dwarf galaxies, potentially solving the cusp-core problem without baryonic effects.

Contribution

It demonstrates that PBHs in the 25-100 solar mass range can naturally create dark matter cores through dynamical heating in dwarf galaxies, with a specific mass fraction threshold.

Findings

Cusp-to-core transition occurs within 1-8 Gyr.

Requires at least 1% PBH dark matter fraction.

Transition time-scale relates to relaxation time.

Abstract

We performed a series of high-resolution $N$-body simulations to examine whether dark matter candidates in the form of primordial black holes (PBHs) can solve the cusp-core problem in low-mass dwarf galaxies. If some fraction of the dark matter in low-mass dwarf galaxies consists of PBHs and the rest is cold dark matter, dynamical heating of the cold dark matter by the PBHs induces a cusp-to-core transition in the total dark matter profile. The mechanism works for PBHs in the 25-100 M$_{\sun}$ mass window, consistent with the LIGO detections, but requires a lower limit on the PBH mass fraction of 1$\%$ of the total dwarf galaxy dark matter content. The cusp-to-core transition time-scale is between 1 and 8 Gyr. This time-scale is also a constant multiple of the relaxation time between cold dark matter particles and PBHs, which depends on the mass, the mass fraction and the scale radius of the initial density profile of PBHs. We conclude that dark matter cores occur naturally in halos comprised of cold dark matter and PBHs, without the need to invoke baryonic processes.