Self-interacting dark matter and core formation in field low-surface-brightness galaxies

TL;DR

This study investigates the role of self-interacting dark matter in forming galaxy cores by analyzing isolated low-surface-brightness galaxies and proto-clusters, suggesting a low cross section is favored.

Contribution

It provides order-of-magnitude estimates indicating a low dark matter self-interaction cross section, excluding higher values without numerical simulations.

Findings

Excludes self-interaction cross section of 1 cm^2/g.

Favours a cross section of 0.1 cm^2/g.

Consistent with cluster core shape constraints.

Abstract

Dark matter may play an important role in galaxy formation through its non-trivial properties. For example, self-interacting dark matter may contribute to the formation of the widely observed core structures in galaxies. However, galaxy formation is a complex process, and such core structures can also arise from baryonic effects within the cold dark matter framework. To clarify the role of dark matter self-interactions, it is necessary to study systems that evolve without significant baryonic disturbances. Low-surface-brightness galaxies in the field, which are gravitationally isolated and have evolved with minimal external influence, are suitable candidates for this purpose. Since these galaxies typically contain only a small amount of baryonic matter, strong baryonic effects are not expected in their evolutionary history. In this study, we assume that these galaxies decoupled from proto-clusters at high redshift. Based on this assumption, we set initial conditions and estimate the time required for core formation, which we compare with the time corresponding to the redshift of proto-clusters. We examine five low-surface-brightness galaxies in the field and three observed proto-clusters at redshifts z=2.45, 7.66 and 7.88. Our analyses, based on order-of-magnitude estimates without numerical simulations, excludes a self-interaction cross section of sigma/m = 1 cm^2/g, while sigma/m = 0.1 cm^2/g is favored. This result is consistent with constraints derived from the shapes of present-day cluster cores.