EDGE: Dark matter core creation depends on the timing of star formation

Claudia Muni; Andrew Pontzen; Justin I. Read; Oscar Agertz; Martin P. Rey; Ethan Taylor; Stacy Y. Kim; Emily I. Gray

doi:10.1093/mnras/stae2748

paper

EDGE: Dark matter core creation depends on the timing of star formation

arXiv:2407.14579 · doi:10.1093/mnras/stae2748

Abstract

We study feedback-driven cold dark matter core creation in the EDGE suite of radiation-hydrodynamical dwarf galaxy simulations. Understanding this process is crucial when using observed dwarf galaxies to constrain the particle nature of dark matter. While previous studies have shown the stellar-mass to halo-mass ratio $(M_{⋆} / M_{200})$ determines the extent of core creation, we find that in low-mass dwarfs there is a crucial additional effect, namely the timing of star formation relative to reionisation. Sustained post-reionisation star formation decreases central dark matter density through potential fluctuations; conversely, pre-reionisation star formation is too short-lived to have such an effect. In fact, large stellar masses accrued prior to reionisation are a strong indicator of early collapse, and therefore indicative of an increased central dark matter density. We parameterise this differentiated effect by considering $M_{⋆, post} / M_{⋆, pre}$ , where the numerator and denominator represent the amount of star formation after and before $z \sim 6.5$ , respectively. Our study covers the halo mass range $1 0^{9} < M_{200} < 1 0^{10} M_{⊙}$ (stellar masses between $1 0^{4} < M_{⋆} < 1 0^{8} M_{⊙}$ ), spanning both ultra-faint and classical dwarfs. In this regime, $M_{⋆, post} / M_{⋆, pre}$ correlates almost perfectly with the central dark matter density at $z = 0$ , even when including simulations with a substantially different variant of feedback and cooling. We provide fitting formulae to describe the newfound dependence.

11 pages, 8 figures, 1 appendix. Accepted for publication in MNRAS

EDGE: Dark matter core creation depends on the timing of star formation

Abstract

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