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

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 $\hat{I}{”}_{\mathrm{z}}$, 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 $\hat{I}{»}_{\mathrm{mfp}}$. AMBER reproduces the free electron number density and the patchy kSZ power spectrum of radiation-hydrodynamic simulations at the target resolution ($1\mathrm{Mpc}/h$) with matched reionization parameters. With a suite of $(2\mathrm{Gpc}/h{)}^3$ simulations using AMBER, we first constrain the redshift midpoint $6.0<z_{\mathrm{mid}}<8.9$ using the Planck2018 Thomson optical depth result (95\% CL). Then, assuming $z_{\mathrm{mid}}=8$, we find that the amplitude of $D_{\ell =3000}^{\mathrm{pkSZ}}$ scales linearly with the duration of reionization $\hat{I}{”}_z$, and is consistent with the $1\ddot{I}ƒ$ upper limit from the South Pole Telescope (SPT) results up to $\hat{I}{”}_z<5.1$ ($\hat{I}{”}_z$ encloses $5\%$ to $95\%$ ionization). Moreover, a shorter $\hat{I}{»}_{\mathrm{mfp}}$ can lead to a $\sim 10\%$ lower $D_{\ell =3000}^{\mathrm{pkSZ}}$ and a flatter slope in the $\hat{I}{”}_z-D_{\ell =3000}^{\mathrm{pkSZ}}$ scaling relation, thereby affecting the constraints on $\hat{I}{”}_z$ at $\ell =3000$. Allowing $z_{\mathrm{mid}}$ and $\hat{I}{»}_{\mathrm{mfp}}$ to vary simultaneously, we get spectra consistent with the SPT result ($95\%$ CL) up to $\hat{I}{”}_z=12.8$ (but $A_z>8$ is needed to ensure an end of reionization before $z=5.5$). We show that constraints on the asymmetry require $\sim 0.1\hat{I}¼k^2$ 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.

20 pages, 17 Figures; comments welcome