A Self-interacting Dark Matter Solution to the Extreme Diversity of Low-mass Halo Properties

Abstract

The properties of low-mass dark matter (DM) halos appear to be remarkably diverse relative to cold, collisionless DM predictions, even in the presence of baryons. We show that self-interacting DM (SIDM) can simultaneously explain observations of halo diversity at two opposite extremes—the inner density profile of the dense substructure perturbing the strong lens galaxy SDSSJ0946+1006 and the rotation curves of isolated, gas-rich ultradiffuse galaxies (UDGs). To achieve this, we present the first cosmological zoom-in simulation featuring strong DM self-interactions in a galaxy group environment centered on a 1013 M ⊙ host halo. In our SIDM simulation, most surviving subhalos of the group-mass host are deeply core-collapsed, yielding excellent candidates for the observed dense strong-lens perturber. Self-interactions simultaneously create kiloparsec-scale cores in low-concentration isolated halos, which could host the observed UDGs. Our scenario can be further tested with observations of DM structure and galaxies over a wide mass range.

Cold Dark Matter and Self-interacting Dark Matter Interpretations of the Strong Gravitational Lensing Object JWST-ER1

“…For a viable SIDM model, the cross section must be velocity dependent, decreasing toward massive halos (Tulin & Yu 2018). Interestingly, in the velocity-dependent SIDM model proposed in Nadler et al (2023) to explain observations of extreme halo diversity, the predicted effective cross section is 0.1 cm 2 g −1 in 10 13 M e halos, consistent with our constraints from the early-type galaxies.…”

Self-interacting Dark Matter Interpretation of Crater II

“…Cosmological N-body simulations show that strong dark matter self-interactions can diversify inner dark matter densities of satellite halos (Zavala et al 2019;Turner et al 2021;Correa et al 2022;Nadler et al 2023;Yang et al 2023a), due to core formation and collapse (Balberg et al 2002;Koda & Shapiro 2011). For σ/m  30-50 cm 2 g −1 in ultrafaint dwarf halos, the collapse could occur within the Hubble time, yielding a high central density.…”

“…The cyan and pink bands denote the 68% credibility intervals for dark matter and stars, respectively, based on a fit to the kinematics of Crater II (Caldwell et al 2017). The data points in the left panel denote the enclosed masses evaluated within R 1/2 and R Nadler et al 2023). The concentration of the Crater II halo is close to the median and hence it is in the core-expansion phase.…”

“…. This condition can be satisfied naturally for velocity-dependent SIDM models that evade the cluster constraints; see, e.g., Yang et al (2023a) and Nadler et al (2023) for examples.…”

A parametric model for self-interacting dark matter halos

“…Compared to collisionless cold dark matter (CDM), SIDM predicts more diverse dark matter distributions in both isolated halos and subhalos, see, e.g., [4,5]. In particular, the phenomenon of gravothermal collapse [6,7] could be probed using observations of the Milky Way satellite galaxies [4,5,[8][9][10][11][12][13][14][15][16] and strong gravitational lensing events [17][18][19][20][21]. The collapsed central halo could also provide a seed for supermassive black holes [22][23][24][25][26][27].…”