Remarks on Dark Matter Constituents with Many Solar Masses

TL;DR

This paper discusses how the actual accretion of normal matter by massive dark matter objects is less than spherical models suggest, affecting constraints on their abundance based on X-ray emissions and the CMB spectrum.

Contribution

It highlights that spherical accretion models overestimate matter accretion and X-ray emissions, leading to overly strict limits on intermediate-mass MACHOs as dark matter candidates.

Findings

Spherical accretion models overestimate matter accretion.

Overestimation affects constraints on MACHO abundance.

Revised models suggest less severe limits.

Abstract

Dark matter constituents of many solar masses will accrete normal matter which emits X-rays that can be downgraded to microwaves which may distort the precisely-measured black-body spectrum of the Cosmic Microwave Background. However, it is known from elsewhere that spherical models of accretion vastly overestimate the amount accreted and consequently the emitted X-rays. Therefore, exclusion plots based on spherical accretion for the allowed fraction of the dark matter versus the MACHO mass give upper limits on intermediate-mass MACHOs which are too severe, sometimes by orders of magnitude.