Dark matter limits from the tip of the red giant branch of globular clusters

TL;DR

This study uses Gaia data to constrain dark matter properties by analyzing the tip of the red giant branch in globular clusters, providing a novel, galaxy-wide independent method that supports the robustness of the TRGB as a standard candle.

Contribution

It introduces a new astrophysical method to constrain dark matter interactions using globular cluster luminosities, complementing Earth-based experiments.

Findings

Constraints on dark matter-nucleon cross section from globular clusters.

Limits are weaker than direct detection but galaxy-wide and independent.

TRGB remains a robust standard candle despite dark matter effects.

Abstract

Capture and annihilation of WIMP-like dark matter in red giant stars can lead to faster-than-expected ignition of the helium core, and thus a lower tip of the red giant branch (TRGB) luminosity. We use Gaia data to place constraints on the dark matter-nucleon cross section using 22 globular clusters with measured TRGB luminosities, and place projections on the sensitivity resulting from 161 clusters with full phase space distributions observed by Gaia. Although limits remain weaker than those from Earth-based direct detection experiments, they represent a constraint that is fully independent of dark matter properties in the Solar neighbourhood, probing its properties across the entire Milky Way galaxy. Based on our findings, it is likely that the use of the TRGB as a standard candle in $H_0$ measurements is very robust against the effects of dark matter.