Exploring delaying and heating effects on the 21-cm signature of fuzzy dark matter

TL;DR

This paper models the 21-cm signal in fuzzy dark matter cosmologies, incorporating delaying and heating effects, to assess the potential for upcoming experiments to distinguish FDM from cold dark matter.

Contribution

It introduces a modified 21cmvFAST code interfaced with CLASS to include all relevant delaying and heating effects in FDM models, enabling comprehensive parameter analysis.

Findings

HERA can detect FDM particles up to ~10^{-19} eV.

Including effects reduces the detectability range.

The model forecasts constraints on FDM and astrophysical parameters.

Abstract

In the fuzzy dark matter (FDM) model, dark matter is composed of ultra-light particles with a de Broglie wavelength of $\sim$kpc, above which it behaves like cold dark matter (CDM). Due to this, FDM suppresses the growth of structure on small scales, which delays the onset of the cosmic dawn (CD) and the subsequent epoch of reionization (EoR). This leaves potential signatures in the sky averaged 21-cm signal (global), as well as in the 21-cm fluctuations, which can be sought for with ongoing and future 21-cm global and intensity mapping experiments. To do so reliably, it is crucial to include effects such as the dark-matter/baryon relative velocity and Lyman-Werner star-formation feedback, which also act as delaying mechanisms, as well as CMB and \lya heating effects, which can significantly change the amplitude and timing of the signal, depending on the strength of X-ray heating sourced by the remnants of the first stars. Here we model the 21-cm signal in FDM cosmologies across CD and EoR using a modified version of the public code 21cmvFAST that accounts for all these additional effects, and is directly interfaced with the Boltzmann code CLASS so that degeneracies between cosmological and astrophysical parameters can be fully explored. We examine the prospects to distinguish between the CDM and FDM models and forecast joint astrophysical, cosmological and FDM parameter constraints achievable with intensity mapping experiments such as HERA and global signal experiments like EDGES. We find that HERA will be able to detect FDM particle masses up to $m_{\rm FDM}\! \sim \!10^{-19}\,{\rm eV}\!-\!10^{-18}\,{\rm eV}$, depending on foreground assumptions, despite the mitigating effect of the delaying and heating mechanisms included in the analysis.