PREPRINT
9FB789F0-4E9A-4E4A-9521-915695D3B6EA

# Exploration of 3D wavelet scattering transform coefficients for line-intensity mapping measurements

Dongwoo T Chung
arXiv:2207.06383

Submitted on 13 July 2022

## Abstract

The wavelet scattering transform (WST) has recently gained attention in the context of large-scale structure studies, being a possible generator of summary statistics encapsulating non-Gaussianities beyond the reach of the conventional power spectrum. This work examines the three-dimensional solid harmonic WST in the context of a three-dimensional line-intensity mapping measurement to be undertaken by current and proposed phases of the CO Mapping Array Project (COMAP). The WST coefficients demonstrate interpretable behaviour in the context of noiseless CO line-intensity simulations. The contribution of the cosmological $z\sim 3$ signal to these coefficients is also detectable in principle even in the Pathfinder phase of COMAP. In Fisher forecasts based on large numbers of simulations that incorporate observational noise, even a reduced 'shapeless' set of $\ell$-averaged WST coefficients show constraining power that can exceed that of the power spectrum alone even with similar detection significance. The full WST could improve parameter constraints even over the combination of the power spectrum and the voxel intensity distribution, showing that it uniquely encapsulates shape information about the line-intensity field. However, practical applications urgently require further understanding of the WST in key contexts like covariances and cross-correlations.

## Preprint

Comment: 14 pages; 4 figures, 5 tables; submitted to MNRAS

Subjects: Astrophysics - Cosmology and Nongalactic Astrophysics; Astrophysics - Instrumentation and Methods for Astrophysics