Detecting the non-Gaussianity of the 21-cm signal during reionization with the wavelet scattering transform
Abstract
Detecting the 21-cm hyperfine transition from neutral hydrogen in the intergalactic medium is our best probe for understanding the astrophysical processes driving the Epoch of Reionization (EoR). The primary means for a detection of this 21-cm signal is through a statistical measurement of the spatial fluctuations using the 21-cm power spectrum (PS). However, the 21-cm signal is non-Gaussian meaning the PS, which only measures the Gaussian fluctuations, is suboptimal for characterizing all of the available information. The upcoming Square Kilometre Array (SKA) will perform a deep, 1000 h observation over 100 deg2 specifically designed to recover direct images of the 21-cm signal. In this work, we use the Wavelet Scattering Transform (WST) to extract the non-Gaussian information directly from these 2D images of the 21-cm signal. The key advantage of the WST is its stability with respect to statistical noise for measuring non-Gaussian information, unlike the bispectrum whose statistical noise diverges. In this work, we specifically focus on introducing a novel method to isolate non-Gaussian information from an image and apply this methodology to individual mock 21-cm images to quantify the strength of the non-Gaussian information contained within a single image. For example, at 150 (177) MHz (z ~ 8.5 and ~7) for a fiducial reionization model we recover a signal to noise of ~5 (8) for the non-Gaussian information assuming perfect foreground removal and ~2 (3) assuming foreground wedge avoidance.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- March 2023
- DOI:
- 10.1093/mnras/stac3822
- arXiv:
- arXiv:2207.09082
- Bibcode:
- 2023MNRAS.519.5288G
- Keywords:
-
- galaxies: high-redshift;
- intergalactic medium;
- dark ages;
- reionization;
- first stars;
- diffuse radiation;
- early Universe;
- cosmology: theory;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 17 pages, 10 figures and 1 table. Submitted to MNRAS, comments welcome