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Relating the kinetic Sunyaev-Zel’dovich effect and the 21 cm signal

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Ivelin Georgiev, Adélie Gorce,

and Garrelt Mellema

What is Cosmic Reionisation?

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Nature.com

Ivelin Georgiev Cosmology in the Alps Paper: 2312.04259 Twitter: reivonization Email: ivelin.georgiev@astro.su.se�

The Epoch of Reionisation (EoR) spans astrophysical & cosmological scales.

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�The 21-cm signal contains ionisation and density information but is a probe of the neutral medium.���Combining different probes will allow us to better constrain the nature of the EoR.

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γ

I_CMB+ΔI

I_CMB

v_gas

The Sunyaev-Zel'dovich effect results from the scattering of CMB photons by free electrons.

The kinetic Sunyaev-Zel’dovich effect

The patchy kSZ will be sensitive to the morphology of reionisation

(e.g. Iliev+06,Mesinger+12).

During EoR CMB photons scatter off ionised bubbles along the LOS.

Ivelin Georgiev Cosmology in the Alps Paper: 2312.04259 Twitter: reivonization Email: ivelin.georgiev@astro.su.se�

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Relating the 21-cm and Electron Density Power Spectra

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Ivelin Georgiev Cosmology in the Alps Paper: 2312.04259 Twitter: reivonization Email: ivelin.georgiev@astro.su.se�

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See 2110.13190 for the 21-cm Decomposition 😉.

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The Simplest model overestimates

the P₂₁ amplitude and duration of the EoR but in a self-consistent manner.

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Ivelin Georgiev Cosmology in the Alps Paper: 2312.04259 Twitter: reivonization Email: ivelin.georgiev@astro.su.se�

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Ivelin Georgiev Cosmology in the Alps Paper: 2312.04259 Twitter: reivonization Email: ivelin.georgiev@astro.su.se�

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The Simplest model overestimates

the P₂₁ amplitude and duration of the EoR but in a self-consistent manner.

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Sample Parameters:

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• z_re : middle of EoR, �
• z_end : end of EoR,�
• α₀ : constant large-scale amplitude P_ee at high-z,�
• κ : typical size of ionised regions during reionisation.

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Gorce et al. 2020

Ivelin Georgiev Cosmology in the Alps Paper: 2312.04259 Twitter: reivonization Email: ivelin.georgiev@astro.su.se�

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P₂₁ is constructed based on the true (z_re , z_end , α₀, k)

Extract best fit values

EoR history is constructed from Gorce+18

Sample parameter space using CosmoMC

P_ee from Gorce et al. 2020�P_δδ from CAMB

P₂₁ and pkSZ are re-constructed

(without the higher-order terms)

χ² statistics analysis

Forecast Overview

Input data & uncertainties

An Intuitive test of the forecast

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We set our goal on early stage detections of P₂₁ .��

P₂₁ data points at z = 6.5, 7.8 for k = 0.5 Mpc^-1 for 1000 h integration time with the SKA.

�One pkSZ data point at l~3000 with a 10% uncertainty, motivated by the observation by Reichardt+21. �

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The pkSZ sensitive to the duration of reionization.��

The 21cm gives us upper limits on z_end and lower limits on z_re.

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Ivelin Georgiev Cosmology in the Alps Paper: 2312.04259 Twitter: reivonization Email: ivelin.georgiev@astro.su.se�

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Increasing the number of 21-cm data points allows us to recover the EoR parameters.

Ivelin Georgiev Cosmology in the Alps Paper: 2312.04259 Twitter: reivonization Email: ivelin.georgiev@astro.su.se�

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LOFAR-MWA Case

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Ivelin Georgiev Cosmology in the Alps Paper: 2312.04259 Twitter: reivonization Email: ivelin.georgiev@astro.su.se�

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Comparison to RSAGE simulations

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Ivelin Georgiev Cosmology in the Alps Paper: 2312.04259 Twitter: reivonization Email: ivelin.georgiev@astro.su.se�

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Constraining/Including the Thomson optical depth

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Ivelin Georgiev Cosmology in the Alps Paper: 2312.04259 Twitter: reivonization Email: ivelin.georgiev@astro.su.se�

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The forecast is naturally complimented by constraints on τ.

A curious side note regarding cross-correlations

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We can re-express the higher-order terms as the cross correlation between the 21-cm field and the density field�

• CO/LAEs can be used as a proxy δ_gal~b δ_ρ,�
• Interesting connection to the 21-cm bias!

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Ivelin Georgiev Cosmology in the Alps Paper: 2312.04259 Twitter: reivonization Email: ivelin.georgiev@astro.su.se�

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Summary & Caveats

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The natural connection between P₂₁ and P_ee allows us to relate the patchy kSZ to the 21-cm signal from the EoR. �

We build a forecast methodology to extract information on the nature of reionisation, given measurements of each data set.��The kSZ data allows us to verify inferences from the 21 cm data.�

The larger the P₂₁ error bars the more degenerate (z_re , z_end , a₀ k).

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Ivelin Georgiev Cosmology in the Alps Paper: 2312.04259 Twitter: reivonization Email: ivelin.georgiev@astro.su.se�

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Extra

Slides :)

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Ivelin Georgiev Cosmology in the Alps Paper: 2312.04259 Twitter: reivonization Email: ivelin.georgiev@astro.su.se�

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SKA 100h

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Ivelin Georgiev Cosmology in the Alps Paper: 2312.04259 Twitter: reivonization Email: ivelin.georgiev@astro.su.se�

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SKA other cases

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Ivelin Georgiev Cosmology in the Alps Paper: 2312.04259 Twitter: reivonization Email: ivelin.georgiev@astro.su.se�

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Discussion on the only cases

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Ivelin Georgiev Cosmology in the Alps Paper: 2312.04259 Twitter: reivonization Email: ivelin.georgiev@astro.su.se�

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Ivelin Georgiev Cosmology in the Alps Paper: 2312.04259 Twitter: reivonization Email: ivelin.georgiev@astro.su.se�

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Ivelin Georgiev Cosmology in the Alps Paper: 2312.04259 Twitter: reivonization Email: ivelin.georgiev@astro.su.se�

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Douspis+2015

Ivelin Georgiev Cosmology in the Alps Paper: 2312.04259 Twitter: reivonization Email: ivelin.georgiev@astro.su.se�

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Gorce+2020

Ivelin Georgiev Cosmology in the Alps Paper: 2312.04259 Twitter: reivonization Email: ivelin.georgiev@astro.su.se�

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Ivelin Georgiev Cosmology in the Alps Paper: 2312.04259 Twitter: reivonization Email: ivelin.georgiev@astro.su.se�

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Ivelin Georgiev Cosmology in the Alps Paper: 2312.04259 Twitter: reivonization Email: ivelin.georgiev@astro.su.se�

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