A possible challenge for Cold and Warm Dark Matter

TL;DR

This paper investigates a unique dark matter halo candidate detected via gravitational lensing, challenging cold dark matter models and suggesting possible self-interacting dark matter or black hole formation.

Contribution

It presents detailed analysis of a novel dark matter structure, proposing that its properties are incompatible with standard cold dark matter but may align with alternative models.

Findings

The object has a point-mass component and an extended mass distribution.

Its properties do not match any known astronomical object.

If dark matter-dominated, it challenges cold dark matter theories.

Abstract

Measuring the density profile and mass concentration of dark-matter haloes is a key test of the standard cold dark matter paradigm. Such objects are dark and thus challenging to characterise, but they can be studied via gravitational lensing. Recently, a million-solar-mass object was discovered superposed on an extended and extremely thin gravitational arc. Here we report on extensive tests of various assumptions for the mass density profile and redshift of this object. We find models that best describe the data have two components: an unresolved point-mass of radius $\leq10$ pc centred on an extended mass distribution with an almost constant surface density out to a truncation radius of 139 pc. These properties do not resemble any known astronomical object. However, if the object is dark matter-dominated, its structure is incompatible with cold dark matter models, but may be compatible with a self-interacting dark matter halo where the central region has collapsed to form a black hole. This detection could thus carry substantial implications for our current understanding of dark matter.