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

Ran Huo,Manoj Kaplinghat,Zhen Pan,Hai-Bo Yu

doi:10.1016/j.physletb.2018.06.024

Abstract

We consider a self-interacting dark matter model in which the massive dark photon mediating the self-interaction 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.

Highlights

The existence of dark matter (DM) in the universe is inferred from its gravitational influence on normal matter
In this Letter, we use this model to explicitly demonstrate how astrophysical observations can pin down the particle physics parameter space. After constraining it to explain the dark matter halos inferred for dwarf galaxies and galaxy clusters, we explore the presence of the damping scale and the dark radiation using the Lyman-α forest, satellite counts, and CMB
We explicitly demonstrate that the kinetic decoupling temperature dictates the deviation of the SIDM matter power spectrum from the standard cold DM (CDM) case and map it to the warm DM (WDM) mass space

Summary

Introduction

The existence of dark matter (DM) in the universe is inferred from its gravitational influence on normal matter. A mass hierarchy between the mediator and the DM particle is required to get a self-scattering cross section that decreases for velocities of O(1000 km/s) (cluster scale) [5] This mediator must decay to avoid the over-closing the universe [13, 14], unless it is (almost) massless (see, e.g., [15, 16]). In this Letter, we use this model to explicitly demonstrate how astrophysical observations can pin down the particle physics parameter space After constraining it to explain the dark matter halos inferred for dwarf galaxies and galaxy clusters, we explore the presence of the damping scale and the dark radiation using the Lyman-α forest, satellite counts, and CMB. A Constrained Simplified SIDM Model We consider a simplified SIDM model with the following interaction La-

Symmetric SIDM Freeze Out

Subhalo Count Disfavored

MM h

Conclusions