Constraints on dark photon dark matter from Lyman-$\alpha$ forest simulations and an ultra-high signal-to-noise quasar spectrum

TL;DR

This paper uses cosmological simulations and high-quality quasar spectra to place constraints on ultralight dark photon dark matter, demonstrating the potential of Lyman-alpha forest data to probe new physics.

Contribution

It introduces a novel flux normalization technique and provides the first robust constraints on dark photon parameters using Lyman-alpha forest data.

Findings

Constraints on dark photon kinetic mixing parameter.

Reconciliation of simulated and observed Lyman-alpha Doppler parameters.

Potential to extend the method to other dark matter scenarios.

Abstract

The ultralight dark photon is a well-motivated, hypothetical dark matter candidate. In a dilute plasma, they can resonantly convert into photons, and heat up the intergalactic medium between galaxies. In this work, we explore the dark photon dark matter parameter space by comparing synthetic Lyman-$\alpha$ forest data from cosmological hydrodynamical simulations to observational data from VLT/UVES of the quasar HE0940-1050 ($z_{\rm em}=3.09$). We use a novel flux normalization technique that targets under-dense gas, reshaping the flux probability distribution. Not only do we place robust constraints on the kinetic mixing parameter of dark photon dark matter, but notably our findings suggest that this model can still reconcile simulated and observed Doppler parameter distributions of $z\sim0$ Lyman-$\alpha$ lines, as seen by HST/COS. This work opens new pathways for the use of the Lyman-$\alpha$ forest to explore new physics, and can be extended to other scenarios such as primordial black hole evaporation, dark matter decay, and annihilation.