A bubble size distribution model for the Epoch of Reionization

Abstract

Aims. The bubble size distribution is a summary statistics that can be computed from the observed 21-cm signal from the Epoch of Reionization. As it depends only on the ionization field and is not limited to gaussian information, it is an interesting probe, complementary to the power spectrum of the full 21-cm signal. Devising a flexible and reliable theoretical model for the bubble size distribution paves the way for using it for astrophysical parameters inference. Methods. The proposed model is built from the excursion set theory and a functional relation between the bubble volume and the collapsed mass in the bubble. Unlike previous models it accommodates any functional relation or distributions. Using parameterized relations allows us to test the predictive power of the model by performing a minimization best-fit to the bubble size distribution obtained from a high resolution, fully coupled radiative hydrodynamics simulations, HIRRAH-21. Results. Our model is able to provide a better fit to the numerical bubble size distribution at ionization fraction of x HII ∼ 1% and 3% than other existing models. Moreover, the bubble volume to collapsed mass relation corresponding to the best-fit parameters, which is not an observable, is compared to numerical simulation data. A good match is obtained, confirming the possibility to infer this relation from an observed bubble size distribution using our model. Finally we present a simple algorithm that empirically implements the process of percolation. We show that it extends the usability of our bubble size distribution model up to x HII ∼ 30%.

Accurate modelling of the Lyman-α coupling for the 21-cm signal, observability with NenuFAR, and SKA

“…Guided by our final goal to be able to robustly model the contribution of the Wouthuysen-Field coupling to the 21-cm signal during the CD, we chose to compare the 3D field of the coupling coefficient x α at fixed redshift, before the back-reaction (which can be evaluated in posttreatment at a negligible CPU cost) in a cosmological simulation box. The various fields that determine x a (source emissivity, neutral gas density, temperature, and velocity of baryonic matter) are provided by a high-resolution radiative hydrodynamics simulation, HIRRAH-21, that resolves halos down to ∼4 × 10 9 M in a 200 h −1 cMpc simulation box (Doussot & Semelin 2022). The native resolution of those fields, 2048 3 , were down sampled to 256 3 (reducing the Monte Carlo noise at 2048 3 resolution would be prohibitively costly).…”

Accurate modelling of the Lyman-$α$ coupling for the 21-cm signal, observability with NenuFAR and SKA

“…Guided by our final goal to be able to robustly model the contribution of the Wouthuysen-Field coupling to the 21-cm signal during the Cosmic Dawn, we choose to compare the three-dimensional field of the coupling coefficient x α at fixed redshift, before back-reaction (which can be evaluated in post-treatment at a negligible CPU cost) in a cosmological simulation box. The various fields that determine x a (source emissivity, neutral gas density, temperature and velocity of baryonic matter) are provided by a high resolution radiative hydrodynamics simulation, HIRRAH-21, that resolves halos down to ∼ 4 × 10 9 M in a 200 h −1 cMpc simulation box (Doussot & Semelin 2022). The native resolution of those fields, 2048 3 , are down sampled to 256 3 (reducing the Monte Carlo noise at 2048 3 resolution would be prohibitively costly).…”