Aspects of Dark Matter Annihilation in Cosmology

Abstract

Cosmic microwave background (CMB) constraints on dark matter annihilation are a uniquely powerful tool in the quest to understand the nature of dark matter. Annihilation of dark matter to Standard Model particles between recombination and reionization heats baryons, ionizes neutral hydrogen, and alters the CMB visibility function. Surprisingly, CMB bounds on dark matter annihilation are not expected to improve significantly with the dramatic improvements in sensitivity expected in future cosmological surveys. In this paper, we will present a simple physical description of the origin of the CMB constraints and explain why they are nearly saturated by current observations. The essential feature is that dark matter annihilation primarily affects the ionization fraction which can only increase substantially at times when the universe was neutral. The resulting change to the CMB occurs on large angular scales and leads to a phenomenology similar to that of the optical depth to reionization. We will demonstrate this impact on the CMB both analytically and numerically. Finally, we will discuss the additional impact that changing the ionization fraction has on large scale structure.

22 pages, 11 figures

References in corpus (8)

• CMB Constraints on WIMP Annihilation: Energy Absorption During the Recombination Epoch
• The 21cm angular-power spectrum from the dark ages
• The Effects of Dark Matter Decay and Annihilation on the High-Redshift 21 cm Background
• Searching for Light Relics with Large-Scale Structure
• The nature of dark matter from the global high redshift HI 21 cm signal
• How Dark Matter Reionized The Universe
• Impact of Dark Matter Annihilation on the High-Redshift Intergalactic Medium
• Dark Matter Interactions, Helium, and the CMB

Cited by in corpus (10)

• The Simons Observatory: Science goals and forecasts
• The Simplest and Most Predictive Model of Muon $g-2$ and Thermal Dark Matter
• Cosmologically Varying Kinetic Mixing
• Dark Stars Powered by Self-Interacting Dark Matter
• Enlightening the dark ages with dark matter
• Manifesting hidden dynamics of a sub-component dark matter
• Dark Initial State Radiation and the Kinetic Mixing Portal
• The Glow of Axion Quark Nugget Dark Matter: (I) Large Scale Structures
• Visualizing Invisible Dark Matter Annihilation with the CMB and Matter Power Spectrum
• The Bactrian Effect: Multiple Resonances and Light Dirac Dark Matter