Dwarf galaxies in CDM and SIDM with baryons: observational probes of the nature of dark matter

Abstract

We present the first cosmological simulations of dwarf galaxies, which include dark matter self-interactions and baryons. We study two dwarf galaxies within cold dark matter, and four different elastic self-interacting scenarios with constant and velocity-dependent cross sections, motivated by a new force in the hidden dark matter sector. Our highest resolution simulation has a baryonic mass resolution of 1.8 × 10 2 M and a gravitational softening length of 34 pc at z = 0. In this first study we focus on the regime of mostly isolated dwarf galaxies with halo masses ∼ 10 10 M where dark matter dynamically dominates even at sub-kpc scales. We find that while the global properties of galaxies of this scale are minimally affected by allowed self-interactions, their internal structures change significantly if the cross section is large enough within the inner sub-kpc region. In these dark-matter-dominated systems, selfscattering ties the shape of the stellar distribution to that of the dark matter distribution. In particular, we find that the stellar core radius is closely related to the dark matter core radius generated by self-interactions. Dark matter collisions lead to dwarf galaxies with larger stellar cores and smaller stellar central densities compared to the cold dark matter case. The central metallicity within 1 kpc is also larger by up to ∼ 15% in the former case. We conclude that the mass distribution, and characteristics of the central stars in dwarf galaxies can potentially be used to probe the self-interacting nature of dark matter.

NIHAO – IV: core creation and destruction in dark matter density profiles across cosmic time

“…This cusp-core controversy suggests that either a modification of the whole CDM paradigm is required (e.g., self interacting dark matter, SIDM, Vogelsberger et al 2014), or the inadequacy of pure N-body simulations to capture the dark matter dynamics on small scales, due to the absence of dissipative phenomena connected to baryonic physics.…”

A Testable Conspiracy: Simulating Baryonic Effects on Self-interacting Dark Matter Halos

“…This is because many of these galaxies are observed to have cores on roughly the scales that are expected in SIDM (Flores & Primack 1994;Moore 1994;de Blok et al 1996;Salucci & Burkert 2000;de Blok et al 2001;Swaters et al 2003;Gentile et al 2004;Simon et al 2005;Spekkens et al 2005;de Blok et al 2008;Kuzio de Naray et al 2008;Donato et al 2009;Oh et al 2011;Adams et al 2014), as opposed to the cusps predicted in dissipationless CDM simulations (Dubinski & Carlberg 1991;Navarro et al 1997). SIDM cores also may provide a natural explanation for the unexpectedly low densities of local dwarf galaxies (Vogelsberger et al 2012(Vogelsberger et al , 2014Elbert et al 2015), which is a problem known as "Too Big to Fail" (TBTF; Boylan-Kolchin et al 2011Ferrero et al 2012;Garrison-Kimmel et al 2014;Tollerud et al 2014;Klypin et al 2015;Papastergis et al 2015). There are many in the galaxy formation community who believe these issues may be resolved by baryonic processes, such as supernova feedback (Navarro et al 1996;Read & Gilmore 2005;Governato et al 2012;Di Cintio et al 2014;Maxwell et al 2015;Oñorbe et al 2015;Dutton et al 2016;Read et al 2016;Katz et al 2017), though not all authors necessarily agree (Peñarrubia et al 2012;Garrison-...…”

Density profile of dark matter haloes and galaxies in the horizon–agn simulation: the impact of AGN feedback

“…This so-called "cusp-core problem" could imply that the CDM paradigm needs to be revised to account for dark matter self-interaction (Yoshida et al 2000;Burkert 2000;Kochanek & White 2000;Spergel & Steinhardt 2000;Davé et al 2001;Ahn & Shapiro 2005;Vogelsberger et al 2014b, Elbert et al 2015Lin & Loeb 2016), a warmer dark matter candidate (Colín et al 2000;Bode et al 2001, Lovell et al 2012 or an ultralight axion-particle (e.g., Marsh & Pop 2015), and/or a more exotic coupling between dark matter and dark energy (e.g. Macciò et al 2015).…”