Fuzzy Dark Matter and the 21cm Power Spectrum

TL;DR

This paper models the 21cm power spectrum in fuzzy dark matter cosmologies, showing how FDM alters the timing and amplitude of fluctuations during Cosmic Dawn and EoR, and forecasts HERA's ability to distinguish FDM from CDM.

Contribution

It introduces a detailed model of the 21cm power spectrum in FDM scenarios and assesses the observational prospects for differentiating FDM from CDM using upcoming measurements.

Findings

FDM delays the onset of Cosmic Dawn and EoR compared to CDM.

FDM increases the amplitude of 21cm fluctuations due to enhanced halo bias.

HERA can constrain FDM particle mass to within 20% if FDM is the dominant dark matter component.

Abstract

We model the 21cm power spectrum across the Cosmic Dawn and the Epoch of Reionization (EoR) in fuzzy dark matter (FDM) cosmologies. The suppression of small mass halos in FDM models leads to a delay in the onset redshift of these epochs relative to cold dark matter (CDM) scenarios. This strongly impacts the 21cm power spectrum and its redshift evolution. The 21cm power spectrum at a given stage of the EoR/Cosmic Dawn process is also modified: in general, the amplitude of 21cm fluctuations is boosted by the enhanced bias factor of galaxy hosting halos in FDM. We forecast the prospects for discriminating between CDM and FDM with upcoming power spectrum measurements from HERA, accounting for degeneracies between astrophysical parameters and dark matter properties. If FDM constitutes the entirety of the dark matter and the FDM particle mass is 10-21eV, HERA can determine the mass to within 20 percent at 2-sigma confidence.