Patchy Kinetic Sunyaev-Zel'dovich Effect with Controlled Reionization History and Morphology

TL;DR

This paper introduces a new semi-numerical code, AMBER, to model the patchy kinetic Sunyaev-Zel'dovich effect, exploring how reionization history and morphology influence the kSZ signal and constraining reionization parameters with simulations and observational data.

Contribution

The paper presents the novel AMBER code that accurately models the patchy kSZ effect and systematically investigates the impact of reionization parameters on the kSZ power spectrum.

Findings

Reionization midpoint constrained to 6.0<z_mid<8.9 using Planck data.

kSZ amplitude at l=3000 scales linearly with reionization duration Δz.

Shorter mean free path λ_mfp reduces kSZ power and affects reionization constraints.

Abstract

Using the novel semi-numerical code for reionization AMBER, we model the patchy kinetic Sunyaev-Zel'dovich (kSZ) effect by directly specifying the reionization history with the redshift midpoint $z_\mathrm{mid}$, duration $\Delta_\mathrm{z}$, and asymmetry $A_\mathrm{z}$. We further control the ionizing sources and radiation through the minimum halo mass $M_\mathrm{h}$ and the radiation mean free path $\lambda_\mathrm{mfp}$. AMBER reproduces the free electron number density and the patchy kSZ power spectrum of radiation-hydrodynamic simulations at the target resolution ($1\,{\rm Mpc}/h$) with matched reionization parameters. With a suite of $(2\,{\rm Gpc}/h)^3$ simulations using AMBER, we first constrain the redshift midpoint $6.0<z_{\rm mid}<8.9$ using the Planck2018 Thomson optical depth result (95\% CL). Then, assuming $z_{\rm mid}=8$, we find that the amplitude of $D^{\rm pkSZ}_{\ell=3000}$ scales linearly with the duration of reionization $\Delta_z$, and is consistent with the $1\sigma$ upper limit from the South Pole Telescope (SPT) results up to $\Delta_z<5.1$ ($\Delta_z$ encloses $5\%$ to $95\%$ ionization). Moreover, a shorter $\lambda_{\rm mfp}$ can lead to a $\sim 10\%$ lower $D^{\rm pkSZ}_{\ell=3000}$ and a flatter slope in the $\Delta_z-D^{\rm pkSZ}_{\ell=3000}$ scaling relation, thereby affecting the constraints on $\Delta_z$ at $\ell=3000$. Allowing $z_{\rm mid}$ and $\lambda_{\rm mfp}$ to vary simultaneously, we get spectra consistent with the SPT result ($95\%$ CL) up to $\Delta_z=12.8$ (but $A_z>8$ is needed to ensure an end of reionization before $z=5.5$). We show that constraints on the asymmetry require $\sim 0.1\,\mu k^2$ measurement accuracy at multipoles other than $\ell=3000$. Finally, we find that the amplitude and shape of the kSZ spectrum are only weakly sensitive to $M_h$ under a fixed reionization history and radiation mean-free path.