Using the sample variance of 21 cm maps as a tracer of the ionisation topology

Gorce, Adélie; Hutter, Anne; Pritchard, Jonathan R.

doi:10.1051/0004-6361/202140515

Cited by 10 publications

(5 citation statements)

References 56 publications

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“…In addition to these, a method based on the Betti numbers [67,68] provide the number of connected regions, tunnels and cavities to describe the state of the IGM. A recent study of [69] used a method of local variance which probes the reionization history of the observed patches of the sky as well as trace the ionization morphology. However, in most of these earlier works it is widely been considered that modelled reionizing sources are standard fiducial in nature and the inference drawn through these methods depend on the detection of a large number of Hii regions at any stage consisting of wide variety of sizes.…”

Section: Introductionmentioning

confidence: 99%

Distinguishing reionization models using the largest cluster statistics of the 21-cm maps

Aadarsh

Bag

Dasgupta

et al. 2022

J. Cosmol. Astropart. Phys.

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The evolution of topology and morphology of ionized or neutral hydrogen during different stages of the Epoch of Reionization (EoR) have the potential to provide us a great amount of information about the properties of the ionizing sources during this era. We compare a variety of reionization source models in terms of the geometrical properties of the ionized regions. We show that the percolation transition in the ionized hydrogen, as studied by tracing the evolution of the Largest Cluster Statistics (LCS), is a robust statistic that can distinguish the fundamentally different scenarios — inside-out and outside-in reionization. Particularly, the global neutral fraction at the onset of percolation is significantly higher for the inside-out scenario as compared to that for the outside-in reionization. In complementary to percolation analysis, we explore the shape and morphology of the ionized regions as they evolve in different reionization models in terms of the Shapefinders (SFs) that are ratios of the Minkowski functionals (MFs). The shape distribution can readily discern the reionization scenario with extreme non-uniform recombination in the IGM, such as the clumping model. In the rest of the reionization models, the largest ionized region abruptly grows only in terms of its third SF — 'length' — during percolation while the first two SFs — 'thickness' and 'breadth' — almost remain stable. Thus the ionized hydrogen in these scenarios becomes highly filamentary near percolation and exhibit a 'characteristic cross-section' that varies among the source models. Therefore, the geometrical studies based on SFs, together with the percolation analysis can shed light on the reionization sources.

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Section: Introductionmentioning

confidence: 99%

Distinguishing reionization models using the largest cluster statistics of the 21-cm maps

Aadarsh

Bag

Dasgupta

et al. 2022

J. Cosmol. Astropart. Phys.

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“…Some works considered variance and skewness of PDF of 21cm fluctuations, which are higher-order moments of PDF (e.g. Watkinson & Pritchard 2014Shimabukuro et al 2015;Gorce et al 2021). The variance is the expectation of the squared deviation of a random variable from its mean value and the skewness is a measure of the asymmetry of PDF of a variable.…”

Section: One-point Statisticsmentioning

confidence: 99%

Exploring the cosmic dawn and epoch of reionization with 21cm line

Shimabukuro,

Hasegawa,

Kuchinomachi

et al. 2023

Preprint

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The dark age of the universe, when no luminous object had existed, ended with the birth of the first stars, galaxies, and blackholes. This epoch is called cosmic dawn. Cosmic reionization is the major transition of the intergalactic medium (IGM) in the universe driven by ionizing photons emitted from luminous objects. Although the epoch through the dark age to reionization is a milestone in the universe, our knowledge of this epoch has not been sufficient yet. Cosmic 21cm signal, which is emitted from neutral hydrogen, is expected to open a new window for this epoch. In this review paper, we first introduce the basic physics of the 21cm line and how first stars impact on the 21cm line signal. Next, we briefly summarize how we extract astrophysical information from the 21cm line signal by means of statistical and machine learning approaches. We also discuss the synergy between the 21cm line signal and other emission lines. Finally, we summarize the current status of 21cm experiments.

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“…Along with these, granulometry [76] and persistence theory [77] has also been used for analyzing the topological phases of ionized hydrogen (Hii) regions during the EoR. Analyses involving the theory of Betti numbers [78,79] and local variance [80] focus on the topology like the connectivity, genus and surface area to quantify the IGM state.…”

Section: Jcap05(2023)014mentioning

confidence: 99%

Interpreting the Hi 21-cm cosmology maps through Largest Cluster Statistics. Part I. Impact of the synthetic SKA1-Low observations

Dasgupta

Kumar

Bag

et al. 2023

J. Cosmol. Astropart. Phys.

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We analyse the evolution of the largest ionized region using the topological and morphological evolution of the redshifted 21-cm signal coming from the neutral hydrogen distribution during the different stages of reionization. For this analysis, we use the “Largest Cluster Statistics” — LCS. We mainly study the impact of the array synthesized beam on the LCS analysis of the 21-cm signal considering the upcoming low-frequency Square Kilometer Array (SKA1-Low) observations using a realistic simulation for such observation based on the 21cmE2E-pipeline using OSKAR. We find that bias in LCS estimation is introduced in synthetic observations due to the array beam. This in turn shifts the apparent percolation transition point towards the later stages of reionization. The biased estimates of LCS, occurring due to the effect of the lower resolution (lack of longer baselines) and the telescope synthesized beam will lead to a biased interpretation of the reionization history. This is important to note while interpreting any future 21-cm signal images from upcoming or future telescopes like the SKA, HERA, etc. We conclude that one may need denser uv-coverage at longer baselines for a better deconvolution of the array synthesized beam from the 21-cm images and a relatively unbiased estimate of LCS from such images.

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Using the sample variance of 21 cm maps as a tracer of the ionisation topology

Cited by 10 publications

References 56 publications

Distinguishing reionization models using the largest cluster statistics of the 21-cm maps

Distinguishing reionization models using the largest cluster statistics of the 21-cm maps

Exploring the cosmic dawn and epoch of reionization with 21cm line

Interpreting the Hi 21-cm cosmology maps through Largest Cluster Statistics. Part I. Impact of the synthetic SKA1-Low observations

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