A Halo Model Approach to the $21\mathrm{cm}$ and $\mathrm{Ly}\alpha$ Cross-correlation

Abstract

We present a halo-model-based approach to calculate the cross-correlation between $21\mathrm{cm}$ HI intensity fluctuations and $\mathrm{Ly}\alpha$ emitters (LAE) during the epoch of reionization (EoR). Ionizing radiation around dark matter halos are modeled as bubbles with the size and growth determined based on the reionization photon production, among other physical parameters. The cross-correlation shows a clear negative-to-positive transition, associated with transition from ionized to neutral hydrogen in the intergalactic medium during EoR. The cross-correlation is subject to several foreground contaminants, including foreground radio point sources important for $21\mathrm{cm}$ experiments and low-$z$ interloper emission lines, such as $\mathrm{H}\alpha$, OIII, and OII, for $\mathrm{Ly}\alpha$ experiments. Our calculations show that by masking out high fluxes in the $\mathrm{Ly}\alpha$ measurement, the correlated foreground contamination on the $21\mathrm{cm}$-$\mathrm{Ly}\alpha$ cross-correlation can be dramatically reduced. We forecast the detectability of $21\mathrm{cm}$-$\mathrm{Ly}\alpha$ cross-correlation at different redshifts and adopt a Fisher matrix approach to estimate uncertainties on the key EoR parameters that have not been well constrained by other observations of reionization. This halo-model-based approach enables us to explore the EoR parameter space rapidly for different $21\mathrm{cm}$ and $\mathrm{Ly}\alpha$ experiments.

13 pages, 17 figures. Version accepted for publication in ApJ

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• Detectability of 21cm-signal during the Epoch of Reionization with 21cm-Lyman-$\alpha$ emitter cross-correlation. I
• The Halo Void (Dust) Model of Large Scale Structure
• Coupling parsec and gigaparsec scales: primordial non-Gaussianity with multi-tracer intensity mapping
• LIMFAST. II. Line Intensity Mapping as a Probe of High-Redshift Galaxy Formation
• Exploring the cosmic dawn and epoch of reionization with 21cm line
• Quantifying Density-Ionization Correlations with the 21cm Power Spectrum
• Detectability of 21cm-signal during the Epoch of Reionization with 21cm-Lyman-α emitter cross-correlation. II. Foreground contamination
• Probing delayed-end reionization histories with the 21cm-LAE cross-power spectrum
• Estimating the Feasibility of 21cm-Ly$\alpha$ Synergies using the Hydrogen Epoch of Reionization Array
• Predicting 21cm-line map from Lyman $\alpha$ emitter distribution with Generative Adversarial Networks
• Detectability of 21cm signal during the Epoch of Reionization with 21cm-Lyman-$\alpha$ emitter cross-correlation. III. Model dependence
• Detecting Electron Density Fluctuations from Cosmic Microwave Background Polarization using a Bispectrum Approach
• Probing the Epoch of Reionization using synergies of line intensity mapping
• Prospects for measuring neutrino mass with 21-cm forest
• Analytical modeling of the one-dimensional power spectrum of 21-cm forest based on a halo model method