Impact of dark matter distribution on neutron star properties

TL;DR

This paper explores how dark matter distribution affects neutron star structure and observables, revealing that higher dark matter concentration leads to more compact and less deformable neutron stars, with observational data constraining dark matter parameters.

Contribution

It introduces a combined equation of state incorporating dark matter with baryonic matter, analyzing the impact of dark matter density profiles on neutron star properties using multiple models.

Findings

Increased dark matter concentration enhances neutron star compactness.

Steep dark matter density profiles confine dark matter to the core, affecting star deformability.

Observational data constrains dark matter parameters within neutron star models.

Abstract

We investigate the structural and observable impacts of dark matter (DM) on neutron stars using a combined equation of state that integrates the relativistic mean field (RMF) model for baryonic matter with a variable density profile for DM, incorporating DM-baryon interactions mediated by the Higgs field. Employing three RMF parameter sets (NL3, BigApple, and IOPB-I) for baryonic matter, we analyze mass-radius relations, maximum mass, and tidal deformability, focusing on DM density scaling ($\alpha$) and steepness ($\beta$) parameters. Our findings reveal that increased DM concentration significantly enhances NS compactness, shifting mass-radius profiles and reducing tidal deformability. The DM influence strongly depends on the steepness of the DM density profile, where high $\beta$ values lead to strongly confined DM within the NS core, resulting in more compact and less deformable configurations. Observational constraints from PSR J0740+6620 and GW170817 impose consistent structural limits on DM fractions across different equations of state models, narrowing the allowable parameter space for DM and linking specific combinations of $\alpha M_{\chi}$ ($M_{\chi}$ being the mass of dark matter particle) and $\beta$ values to viable NS structures. This study highlights the interplay among DM concentration, nuclear stiffness, and observational data in shaping NS structure, offering insights into future constraints on DM in high-density astrophysical environments.