Quantifying density-ionization correlations with the 21-cm power spectrum

Pagano, Michael; Liu, Adrian

doi:10.1093/mnras/staa2118

Cited by 17 publications

(12 citation statements)

References 52 publications

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“…In order to extend the physical scenarios bracketed by the astrophysical parameters to outside-in morphologies, we need to modify the simulation. This procedure was the focus of previous work in Watkinson & Pritchard (2014) and Pagano & Liu (2020). We briefly reproduce it here.…”

Section: Eor Simulationmentioning

confidence: 99%

“…The type of correlation between these fields need not be binary, and can vary in position and as a function of redshift resulting in correlations between 𝛿 and 𝑥 HII with statistical combinations of inside-out and outside-in (Furlanetto & Oh 2005;Madau & Haardt 2015). A method to parametrize the correlation between these fields has previously been proposed by Pagano & Liu (2020).…”

Section: Introductionmentioning

confidence: 99%

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Lyman Alpha Emitters and the 21cm Power Spectrum as Probes of Density-Ionization Correlation in the Epoch of Reionization

Pagano,

Liu

2021

Preprint

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Due to the large cross section of Ly𝛼 photons with hydrogen, Lyman Alpha Emitters (LAEs) are sensitive to the presence of neutral hydrogen in the intergalactic medium (IGM) during the Epoch of Reionization (EoR): the period in the Universe's history where neutral hydrogen in the IGM is ionized. The correlation of the ionized regions in the IGM with respect to the underlying intrinsic LAEs has a pronounced effect on the number of observed LAEs and their apparent clustering. As a result, observations of LAEs during the EoR can be used as a probe of the EoR morphology. Here we build on previous works where we parametrize the density-ionisation correlation during the EoR, and study how the observed number density and angular correlation function (ACF) of LAEs depends on this parametrization. Using Subaru measurements of the number density of LAEs and their ACF at z = 6.6, we place constraints on the EoR morphology. We find that measurements of LAEs at z = 6.6 alone cannot distinguish between different density-ionization models at 68% credibility. However, adding information regarding the number density, and ACF, of LAEs at 𝑧 = 6.6 to 21cm power spectrum measurements using the hydrogen Epoch of Reionization Array (HERA) at the midpoint of reionization can rule out uncorrelated and outside-in reionization at 99% credibility.

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Section: Eor Simulationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Lyman Alpha Emitters and the 21cm Power Spectrum as Probes of Density-Ionization Correlation in the Epoch of Reionization

Pagano,

Liu

2021

Preprint

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“…The SKA will produce 2D tomographic images of the 21 cm emission of the EoR at many redshifts. Geometrical studies can therefore focus directly on the 21 cm fields, for example, using the 21 cm power spectrum (see Kim et al 2013;Choudhury & Paranjape 2018;Seiler et al 2019;Pagano & Liu 2020) or the 21 cm bispectrum (see Hutter et al 2020) to extract topological information, such as the size distribution of ionised bubbles.…”

Section: Introductionmentioning

confidence: 99%

First look at the topology of reionisation redshifts in models of the epoch of reionisation

Thélie

Aubert

Gillet

et al. 2022

A&A

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Context. During the epoch of reionisation (EoR), the first stars and galaxies appeared while creating ionised bubbles that eventually percolated near z ∼ 6. These ionised bubbles and percolation process are closely scrutinised today because observations of neutral hydrogen will be carried on in the next decade with the Square Kilometre Array radio telescope, for instance. In the meantime, EoR studies are performed in semi-analytical and fully numerical cosmological simulations to investigate the topology of the process, for instance. Aims. We analyse the topology of EoR models by studying regions that are under the radiative influence of ionisation sources. These regions are associated with peak patches of the reionisation redshift field, for which we measure the general properties such as their number, size, shape, and orientation. We aim to gain insights into the geometry of the reionisation process and its relation to the matter distribution, for example. We also assess how these measurements can be used to quantify the effect of physical parameters on the EoR models or the differences between fully numerical simulations and semi-analytical models. Methods. We used the framework of Morse theory and persistent homology in the context of the EoR, which was investigated via the DisPerSE algorithm on gas density and redshift of reionisation maps. We analysed different EoR scenarios with semi-analytical 21cmFAST and fully numerical EMMA simulations. Results. We can distinguish between EoR models with different sources using simple analyses of the number, shape, and size distributions of the reionisation redshift patches. For every model (of the semi-analytical and fully numerical simulations), we statistically show that these bubbles are rather prolate and aligned with the underlying gas filaments. Moreover, we briefly highlight that the percolation process of HII bubbles during the EoR can be followed by studying the reionisation redshift fields with different persistence thresholds. Finally, we show that fully numerical EMMA simulations can be made consistent with 21cmFAST models in this topological framework as long as the source distribution is diffuse enough.

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“…Note that in this section, we effectively have made a physical argument about the nature of reionization, namely, that it occurs "inside out." Though this choice departs from our effort to avoid explicit astrophysical assumptions, it is appropriate for comparisons to 21cmfast, and could be generalized in the future (see, e.g., Pagano & Liu, 2020, for one approach). Fortunately, scenarios with a strong degree of anti-correlation between ionization and density fields generate stronger 21-cm fluctuations than the alternative, and should thus be easier to rule out as upper limits become more stringent (Pagano & Liu, 2020.…”

Section: Model For the Density Of Bubble Materialsmentioning

confidence: 99%

A galaxy-free phenomenological model for the 21-cm power spectrum during reionization

Mirocha,

Muñoz,

Furlanetto

et al. 2022

Preprint

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Upper limits from the current generation of interferometers targeting 21-cm emission from high redshifts have recently begun to rule out physically realistic, though still extreme, models of the Epoch of Reionization (EoR). While inferring the detailed properties of the first galaxies is one of the most important motivations for 21-cm measurements, they can also provide useful constraints on the properties of the intergalactic medium (IGM). Motivated by this, we build a simple, phenomenological model for 21-cm fluctuations that works directly in terms of IGM properties, which bypasses the computationally expensive 3-D semi-numerical modeling generally employed in inference pipelines and avoids explicit assumptions about galaxy properties. The key simplifying assumptions are that (i) the ionization field is binary, and composed of spherical bubbles with an abundance described well by a parametric bubble size distribution, and (ii) that the spin temperature of the "bulk" IGM outside bubbles is uniform. Despite the simplicity of the model, the mean ionized fraction and spin temperature of the IGM recovered from mock 21-cm power spectra generated with 21cmfast are in qualitative agreement with the true input values. This suggests that it is possible to obtain comparable constraints on the IGM from 21-cm measurements using models with very different assumptions, parameters, and priors. Our approach will thus be complementary to semi-numerical models as upper limits continue to improve in the coming years.

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Quantifying density-ionization correlations with the 21-cm power spectrum

Cited by 17 publications

References 52 publications

Lyman Alpha Emitters and the 21cm Power Spectrum as Probes of Density-Ionization Correlation in the Epoch of Reionization

Lyman Alpha Emitters and the 21cm Power Spectrum as Probes of Density-Ionization Correlation in the Epoch of Reionization

First look at the topology of reionisation redshifts in models of the epoch of reionisation

A galaxy-free phenomenological model for the 21-cm power spectrum during reionization

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