Constraining Dissipative Dark Matter Self-Interactions

Abstract

We study the gravothermal evolution of dark matter halos in the presence of dissipative dark matter self-interactions. Dissipative interactions are present in many particle-physics realizations of the dark-sector paradigm and can significantly accelerate the gravothermal collapse of halos compared to purely elastic dark matter self-interactions. This is the case even when the dissipative interaction timescale is longer than the free-fall time of the halo. Using a semi-analytical fluid model calibrated with isolated and cosmological N -body simulations, we calculate the evolution of the halo properties -including its density profile and velocity dispersion profile -as well as the core-collapse time as a function of the particle model parameters that describe the interactions. A key property is that the inner density profile at late times becomes cuspy again. Using 21 dwarf galaxies that exhibit a core-like dark matter density profile, we derive constraints on the strength of the dissipative interactions and the energy loss per collision.

Early formation of supermassive black holes via dark matter self-interactions

“…The mass in the central region quickly contracts, leading to a flattening of M (r), the mass enclosed within radius r, shown in figure 1). These qualitative observations are consistent with the results of hydrodynamical treatments, where the halo shows very little change over most of its history, followed by a sudden contraction [6,42].…”

“…At the other extreme, if v c is too low, very little energy is lost in the collisions, making the inelasticity less effective. This could lead to gravothermal collapse in dwarf galaxies or low surface brightness galaxies (LSBs) resulting in cuspy DM profiles [42] contrary to perceptions that these systems have cored profiles [26][27][28][29][30][31][32]. On the other hand there is evidence suggesting that not all dwarf spheroidals are cored [35,51,52].…”

“…The time required for collapse is thus greatly reduced relative to that found for elastically scattering DM, consistent with the results found by refs. [13,42]. However direct comparison with previous studies is hampered by key differences between the approaches.…”

“…Ref. [42] also considered the gravothermal collapse of a halo of dissipative DM, but for a single-component model with f = 1. Constraints on the cross section are derived by demanding that gravothermal collapse does not occur in dwarf galaxies and low surface brightness galaxies (LSBs), which would create cuspy density profiles unlike those that are observed in some systems.…”

Co-interacting dark matter

“…1, in the region below the solid intersection lines, the friction induced by plasma collision is not significant enough to change A energy density. Moreover, at large g , ψ can dissipate its energy via A emission ψψ → ψψA [77,78], and we found that the effect is small at both early universe and late time for the parameter space we considered. In summary, the g is small enough that both heating via A absorption or cooling via A emission are negligible.…”