Abstract
Abstract We investigate the response of self-interacting dark matter (SIDM) halos to the growth of galaxy potentials using idealized simulations, with each run in tandem with collisionless cold dark matter (CDM). We find that if the stellar potential strongly dominates in the central parts of a galaxy, then SIDM halos can be as dense as CDM halos on observable scales. For extreme cases, core collapse can occur, leading to SIDM halos that are denser and cuspier than their CDM counterparts. If the stellar potential is not dominant, then SIDM halos retain isothermal cores with densities far below CDM predictions. When a disk is present, the inner SIDM halo becomes more flattened in the disk plane than the CDM halo. These results are in excellent quantitative agreement with the predictions of Kaplinghat et al. We also simulated a cluster halo with a central stellar distribution similar to the brightest central galaxy of the cluster A2667. An SIDM halo simulated with the cross-section over mass provides a good match to the measured dark matter (DM) density profile, while an adiabatically contracted CDM halo is denser and cuspier. The profile of the same halo simulated with is not dense enough. Our findings are in agreement with previous results that is disfavored for DM collision velocities above about 1500 km s−1. More generally, the interaction between baryonic potentials and SIDM densities offers new directions for constraining SIDM cross-sections in galaxies where baryons are dynamically important.
Highlights
The dark matter (DM) paradigm has been tremendously successful in explaining the large-scale structure of our universe, though the precise nature of DM remains unknown
Collisional or self-interacting dark matter (SIDM) was first explored in the context of galaxy formation by Spergel & Steinhardt (2000), who argued that SIDM models with the cross-section over mass s m ~ 1 cm2 g-1 should lead to observable constant-density cores in galaxies, which is in agreement with observations at that time
Fiducial, and Compact Disk potentials. These show that the SIDM halo, resulting in a much higher central density than even the contracted cold dark matter (CDM) halo
Summary
The dark matter (DM) paradigm has been tremendously successful in explaining the large-scale structure of our universe (see, e.g., Planck Collaboration et al 2016; Rodríguez-Torres et al 2016), though the precise nature of DM remains unknown. The simplest example of cold dark matter (CDM), consisting of a single, collisionless particle with negligible primordial thermal velocity dispersion, can match the large-scale data remarkably well. Collisional or self-interacting dark matter (SIDM) was first explored in the context of galaxy formation by Spergel & Steinhardt (2000), who argued that SIDM models with the cross-section over mass s m ~ 1 cm g-1 should lead to observable constant-density cores in galaxies, which is in agreement with observations at that time. While early estimates suggested that SIDM models of this kind would significantly reduce substructure counts compared to CDM, more recent numerical investigations have shown that the substructure differences are minimal (Vogelsberger et al 2012; Rocha et al 2013). The original expectation that SIDM halos should have constant-density cores has been demonstrated robustly in cosmological simulations (Davé et al 2001; Rocha et al 2013; Zavala et al 2013)
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