Influence of tides and self-gravity on Ultra-Light Dark Matter Bounds from Dwarf Galaxies

TL;DR

This paper investigates how tidal interactions and stellar self-gravity influence constraints on ultra-light dark matter from dwarf galaxies, finding that certain ULDM masses remain incompatible with observations.

Contribution

It introduces a method to estimate tidal effects and includes stellar self-gravity in simulations to refine ULDM bounds from dwarf galaxies.

Findings

ULDM masses between 5×10⁻²² and 5×10⁻²¹ eV are still constrained by data.

Tidal interactions can reduce ULDM-induced dynamical heating effects.

Stellar self-gravity can significantly impact the inferred dark matter constraints.

Abstract

Dwarf spheroidal galaxies provide some of the most sensitive astrophysical probes of ultra-light dark matter (ULDM), but the inferred constraints can be affected by two important systematics: tidal interactions with the Milky Way, which reduce ULDM-induced dynamical heating, and stellar self-gravity, which can become relevant if the stellar component was more compact at earlier times. In this work, we attempt to estimate both effects by reconstructing dwarf-galaxy orbital histories in a Milky-Way potential, adopting a simple and approximate tidal-susceptibility diagnostic that we argue provides a conservative description of tidal stripping, and explicitly including stellar self-gravity in our numerical simulations. Within our framework, which we apply to five different dwarf galaxies, we find that ULDM with masses $5\times 10^{-22} \lesssim m/{\rm eV} \lesssim 5\times 10^{-21}$ remains in tension with current data.