Core Formation in Dwarf Halos with Self Interacting Dark Matter: No Fine-Tuning Necessary

Oliver D. Elbert; James S. Bullock; Shea Garrison-Kimmel; Miguel Rocha; Jose Oñorbe; Annika H. G. Peter

doi:10.1093/mnras/stv1470

paper

Core Formation in Dwarf Halos with Self Interacting Dark Matter: No Fine-Tuning Necessary

arXiv:1412.1477 · doi:10.1093/mnras/stv1470

Abstract

We investigate the effect of self-interacting dark matter (SIDM) on the density profiles of $V_{max} ≃ 40 k m s^{- 1}$ isolated dwarf dark matter halos -- the scale of relevance for the too big to fail problem (TBTF) -- using very high-resolution cosmological zoom simulations. Each halo has millions of particles within its virial radius. We find that SIDM models with cross sections per unit mass spanning the range σ/m = $0.5 - 50$ $c m^{2} g^{- 1}$ alleviate TBTF and produce constant density cores of size 300-1000 pc, comparable to the half-light radii of $M_{⋆}$ ~ $1 0^{5 - 7}$ $M_{⊙}$ dwarfs. The largest, lowest density cores develop for cross sections in the middle of this range, σ/m ~ $5 - 10 c m^{2} g^{- 1}$ . Our largest SIDM cross section run (σ/m = $50 c m^{2} g^{- 1}$ ) develops a slightly denser core owing to mild core-collapse behavior, but it remains less dense than the CDM case and retains a constant density core profile. Our work suggests that SIDM cross sections as large or larger than $50 c m^{2} g^{- 1}$ remain viable on velocity scales of dwarf galaxies ( $v_{rms}$ ~ $40 k m s^{- 1}$ ). The range of SIDM cross sections that alleviate TBTF and the cusp/core problem spans at least two orders of magnitude and therefore need not be particularly fine-tuned.

9 pages, 7 figures

Core Formation in Dwarf Halos with Self Interacting Dark Matter: No Fine-Tuning Necessary

Abstract

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