Patchy Kinetic Sunyaev–Zel’dovich Effect with Controlled Reionization History and Morphology

Abstract

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 mid , duration Δ z , and asymmetry A z . We further control the ionizing sources and radiation through the minimum halo mass M h and the radiation mean free path λ mfp . AMBER reproduces the free-electron number density and the patchy kSZ power spectrum of radiation–hydrodynamic simulations at the target resolution (1 Mpc h −1 ) with matched reionization parameters. With a suite of (2 Gpc/ h ) 3 simulations using AMBER, we first constrain the redshift midpoint 6.0 &lt; z mid &lt; 8.9 using the Planck 2018 Thomson optical depth result (95% CL). Then, assuming z mid = 8, we find that the amplitude of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi>D</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="italic">ℓ</mml:mi> <mml:mo>=</mml:mo> <mml:mn>3000</mml:mn> </mml:mrow> <mml:mrow> <mml:mi>pkSZ</mml:mi> </mml:mrow> </mml:msubsup> </mml:math> scales linearly with the duration of reionization Δ z and is consistent with the 1 σ upper limit from South Pole Telescope (SPT) results up to Δ z &lt; 5.1 (Δ z encloses 5%–95% ionization). Moreover, a shorter λ mfp can lead to a ∼10% lower <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi>D</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="italic">ℓ</mml:mi> <mml:mo>=</mml:mo> <mml:mn>3000</mml:mn> </mml:mrow> <mml:mrow> <mml:mi>pkSZ</mml:mi> </mml:mrow> </mml:msubsup> </mml:math> and a flatter slope in the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi>D</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="italic">ℓ</mml:mi> <mml:mo>=</mml:mo> <mml:mn>3000</mml:mn> </mml:mrow> <mml:mrow> <mml:mi>pkSZ</mml:mi> </mml:mrow> </mml:msubsup> <mml:mo>−</mml:mo> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">Δ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>z</mml:mi> </mml:mrow> </mml:msub> </mml:math> scaling relation, thereby affecting the constraints on Δ z at ℓ = 3000. Allowing z mid and λ mfp to vary simultaneously, we get spectra consistent with the SPT result (95% CL) up to Δ z = 12.8 (but A z &gt; 8 is needed to ensure the end of reionization before z = 5.5). We show that constraints on the asymmetry require ∼0.1 μ k 2 measurement accuracy at multipoles other than ℓ = 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.

Topics & Concepts