Possible Supermassive Dark Object Composed of Light Fermionic Gas with an Embedded Neutron Star Core

TL;DR

This paper explores dark matter admixed neutron stars with light fermionic dark matter, revealing they can form supermassive objects with masses comparable to black holes, potentially acting as gravitational seeds.

Contribution

It introduces a model of dark matter admixed neutron stars with light fermionic dark matter, showing they can reach supermassive scales and resemble black holes.

Findings

Maximum mass inversely proportional to dark matter particle mass

Dark matter halos can be comparable to supermassive black holes

Neutron stars may serve as seeds for supermassive dark objects

Abstract

The structure of dark matter admixed neutron stars (DANSs) are investigated, adopting a non-annihilating self-interacting fermionic dark matter (DM) model, with a particular focus on the case of the light DM particle mass $m_D \in [10^{-10}, 1]$ GeV. The DANSs become DM-dominated configurations when $m_D <10^{-1}$ GeV, where a compact neutron star core becomes embedded within an extremely large DM halo. It is found that the maximum mass of DANSs is inversely proportional to $m_{ D}$, approximately as $ 0.627 (\mathrm{GeV/} m_{\rm D})^2 ~\mathrm{M_{\odot}}$, which implies that extremely large masses can be achieved for small $m_{\rm D}$. For $m_D \sim5\times10^{-4}$ GeV, the calculated mass and size of the DM halo can be comparable to those of supermassive black holes such as Sgr A*. Our findings hint at a scenario where neutron stars might serve as strong gravitational seeds for such supermassive dark objects.