Topology of neutral hydrogen distribution with the Square Kilometer Array

TL;DR

This paper discusses how the topology of neutral hydrogen distribution, measured via Minkowski functionals, can be used with SKA data to study large-scale structure, dark energy, and primordial non-Gaussianity across cosmic history.

Contribution

It introduces the application of topological statistics like the genus to HI maps from SKA, highlighting their robustness and potential for cosmological insights.

Findings

Topological measures are more robust than two-point statistics.

SKA's large volume enables high-precision topological analysis.

Topology can serve as a standard ruler for cosmology.

Abstract

Morphology of the complex HI gas distribution can be quantified by statistics like the Minkowski functionals, and can provide a way to statistically study the large scale structure in the HI maps both at low redshifts, and during the epoch of reionization (EoR). At low redshifts, the 21cm emission traces the underlying matter distribution. Topology of the HI gas distribution, as measured by the genus, could be used as a "standard ruler". This enables the determination of distance-redshift relation and also the discrimination of various models of dark energy and of modified gravity. The topological analysis is also sensitive to certain primordial non-Gaussian features. Compared with two-point statistics, the topological statistics are more robust against the nonlinear gravitational evolution, bias, and redshift-space distortion. The HI intensity map observation naturally avoids the sparse sampling distortion, which is an important systematic in optical galaxy survey. The large cosmic volume accessible to SKA would provide unprecedented accuracy using such a measurement... [abridged]