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

In the fuzzy dark matter (FDM) model, dark matter is composed of ultralight particles with a de Broglie wavelength of ∼kpc, above which it behaves like cold dark matter. Due to this, FDM suppresses the growth of structure on small scales, which delays the onset of the cosmic dawn and the subsequent epoch of reionization. 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 cosmic microwave background and Lyman-α 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 cosmic dawn and epoch of reionization 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 cold dark matter 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 demonstrate that HERA will be sensitive to FDM particle masses, most optimistically up to mFDM∼10-19 eV-10-18 eV, depending on foreground assumptions and limited in practice by uncertainty in the astrophysical parameter values, despite the mitigating effect of the delaying and heating mechanisms included in the analysis.