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

Abstract

Intensity mapping of the 21cm signal of neutral hydrogen will yield exciting insights into the Epoch of Reionisation and the nature of the first galaxies. However, the large amount of data that will be generated by the next generation of radio telescopes, such as the Square Kilometre Array (SKA), as well as the numerous observational obstacles to overcome, require analysis techniques tuned to extract the reionisation history and morphology. In this context, we introduce a one-point statistic, to which we refer as the local variance, ${\sigma }_{\mathrm{loc}}$, that describes the distribution of the mean differential 21cm brightness temperatures measured in two-dimensional maps along the frequency direction of a light-cone. The local variance takes advantage of what is usually considered an observational bias, the sample variance. We find the redshift-evolution of the local variance to not only probe the reionisation history of the observed patches of the sky, but also trace the ionisation morphology. This estimator provides a promising tool to constrain the midpoint of reionisation as well as gaining insight into the ionising properties of early galaxies.

14 pages, 14 figures, published in A&A

References in corpus (20)

• UV Luminosity Functions at redshifts z~4 to z~10: 10000 Galaxies from HST Legacy Fields
• Cosmic Reionization and Early Star-Forming Galaxies: A Joint Analysis of New Constraints from Planck and Hubble Space Telescope
• Model-independent evidence in favor of an end to reionization by z~6
• Efficient Simulations of Early Structure Formation and Reionization
• The morphology of HII regions during reionization
• Simulating Cosmic Reionization at Large Scales II: the 21-cm Emission Features and Statistical Signals
• The Scale of the Problem : Recovering Images of Reionization with GMCA
• Exploring reionisation and high-z galaxy observables with recent multi-redshift MWA upper limits on the 21-cm signal
• Detection and extraction of signals from the epoch of reionization using higher order one-point statistics
• Comparing Foreground Removal Techniques for Recovery of the LOFAR-EoR 21cm Power Spectrum
• Recovering the Wedge Modes Lost to 21-cm Foregrounds
• Adding Context to JWST Surveys with Current and Future 21cm Radio Observations
• The Difference PDF of 21-cm Fluctuations: A Powerful Statistical Tool for Probing Cosmic Reionization
• Minimum size of 21-cm simulations
• Constraining the reionization history using deep learning from 21cm tomography with the Square Kilometre Array
• Cosmic Variance of the 21-cm Global Signal
• The spin-temperature dependence of the 21cm -- LAE cross-correlation
• Measuring the Redshift of Reionization with a Modest Array of Low-Frequency Dipoles
• Quantifying Density-Ionization Correlations with the 21cm Power Spectrum
• Quantiles as Robust Probes of Non-Gaussianity in 21-cm Images

Cited by in corpus (6)

• Simulation-Based Inference of Reionization Parameters From 3D Tomographic 21 cm Lightcone Images
• Exploring the cosmic 21-cm signal from the Epoch of Reionisation using the Wavelet Scattering Transform
• Exploring the cosmic dawn and epoch of reionization with 21cm line
• Detecting the non-Gaussianity of the 21-cm signal during reionisation with the Wavelet Scattering Transform
• Distinguishing reionization models using the largest cluster statistics of the 21-cm maps
• Interpreting the HI 21-cm cosmology maps through Largest Cluster Statistics -- I: Impact of the synthetic SKA1-Low observations