Does CMB Distortion Disfavour Intermediate Mass Dark Matter?

TL;DR

This paper examines how constraints from CMB distortions impact the viability of intermediate mass MACHOs as dark matter candidates, highlighting the uncertainties in accretion models and comparing them with SMBH observations.

Contribution

It critically assesses the simplified accretion models used in CMB distortion constraints and suggests IM-MACHOs could still account for all dark matter based on SMBH comparisons.

Findings

CMB distortion constraints depend heavily on accretion model assumptions

Comparison with SMBH observations challenges previous exclusion of IM-MACHOs

IM-MACHOs remain viable dark matter candidates under certain accretion scenarios

Abstract

We investigate the published constraints on MACHOs in the mass region $10^2 - 10^5 M_{\odot}$ and their possible contribution to dark matter. We focus on constraints which rely on the accretion of matter which emits X-rays that can lead, after downgrading to microwaves, to distortion of the CMB spectrum and isotropy. The most questionable step in this chain of arguments is the use of overly simplified accretion models. We compare how the same accretion models apply to X-ray observations from supermassive black holes SMBHs, M87 and Sgr A*. The comparison of these two SMBHs with intermediate mass MACHOs suggests that the latter could, after all, provide the constituents of all the dark matter. We discuss the status of other constraints on IM-MACHOs.