Signatures of self-interacting dark matter in the matter power spectrum and the CMB

Abstract

We consider a self-interacting dark matter model in which the massive dark photon mediating the selfinteraction decays to light dark fermions to avoid over-closing the universe. We find that if the model is constrained to explain the dark matter halos inferred for spiral galaxies and galaxy clusters simultaneously, there is a strong indication that dark matter is produced asymmetrically in the early universe. It also implies the presence of dark radiation, late kinetic decoupling for dark matter, and a suppressed linear power spectrum due to dark acoustic damping. The Lyman-α forest power spectrum measurements put a strong upper limit on the damping scale and the model has little room to reduce the abundances of satellite galaxies. Future observations in the matter power spectrum and the CMB, in tandem with the impact of self-interactions in galactic halos, makes it possible to measure the gauge coupling and masses of the dark sector particles even when signals in conventional dark matter searches are absent.

The Effect of Dark Matter–Dark Radiation Interactions on Halo Abundance: A Press–Schechter Approach

“…In these models, DM particles are strongly coupled to relativistic particles ("dark radiation") in the early universe which results in oscillatory features in their power spectra, analogous to baryonic acoustic oscillations. The damping effect on the power spectra can be characterized by the kinetic decoupling temperature T kd (van den Aarssen et al 2012;Cyr-Racine et al 2016;Huo et al 2018)…”

“…see Boehm et al 2014;Vogelsberger et al 2016;Chacko et al 2016;Brust et al 2017). This rich phenomenology of "interacting" DM models has led several authors to categorize different DM interactions based on their astrophysical predictions (Boehm et al 2002;Cyr-Racine et al 2016;Murgia et al 2017), and study the astrophysical constraints on their model parameters (Vogelsberger et al 2016;Lovell et al 2018;Huo et al 2018;Pan et al 2018;Díaz Rivero et al 2018).…”

Vector self-interacting dark matter

“…The dash-dotted/green curve corresponds to a fit to the low-velocity data points while maintaining a GeV scale mass. Both benchmark models are subject to the requirement that α X is large enough for the W ± to saturate the dark matter relic abundance; see the matter power spectrum constrain the early-universe annihilation of dark matter in the standard self-interacting dark matter scenario [69] 4 . As such, the most viable sidm models typically assume that the dark matter is asymmetric to avoid these bounds.…”

“…The solid/red curve is an estimated fit to the inferred self-interaction cross sections for the astrophysical systems. The dark matter mass m W is chosen to be 60 MeV in order to satisfy constraints on cluster scales [65,69]. The coupling is then fixed by (5.9).…”

Impact of theoretical assumptions in the determination of the neutrino effective number from future CMB measurements

“…Sterile neutrinos [6], gravitational waves [7], axions [8], gravitino decays [9], and self-interacting dark matter [10] (just to name a few) can indeed all modify N eff .…”