Untangling dust emission and cosmic infrared background anisotropies with the scattering transform statistics

¹ School for Physical Sciences, National Institute of Science Education and Research, HBNI Jatni - 752050, India
² Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400094, India
³ Laboratoire de Physique de l’École Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris Cité, 75005 Paris, France
⁴ Laboratoire d’Océanographie Physique et Spatiale (LOPS), Univ. Brest, CNRS, Ifremer, IRD, 29200 Brest, France

^★ Corresponding authors: This email address is being protected from spambots. You need JavaScript enabled to view it. ; This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 2 March 2026
Accepted: 27 May 2026

Abstract

Context. A template-fit approach is often used to separate the Galactic dust emission and the cosmic infrared background (CIB) anisotropies in low H I column density regions using the observational fact that the 21 cm H I line emission from neutral atomic hydrogen and dust are tightly correlated. However, in some regions with molecular hydrogen, diffuse ionised gas, and dark gas, the same approach fails to trace the excess Galactic dust emission.

Aims. We developed and tested a statistical component-separation method to extract the dust signal from the contaminated Planck 353 GHz observations using the scattering covariance (SC) statistics, which is a subclass of scattering transform statistics.

Methods. We first obtained a set CIB maps over 25 square patches, each with a sky area of 222 deg², using the linear correlation of dust and Galactic H I column density map valid in low H I column density regions using the template-fit approach. We then constructed from these 25 maps a generative model of CIB using SC statistics. We finally relied on this generative model to perform a componentseparation of dust and CIB in the Planck data for different sky regions. These separations were achieved by sampling an ensemble of dust maps through pixel-based optimisation, which, when added to the CIB contamination model, verified all the statistics and cross statistics constraints that were estimated directly from the data.

Results. We validated our algorithm and separated the dust emission from the contamination in the Planck 353 GHz observations. We show the results of the recovered dust map for a test sky region where there is a significant difference between the Planck dust map and CSFD map. We found that the Planck dust map has more structure than the CSFD map. We compared the power spectrum of the recovered dust map and H I map and found a difference in slope (∆α ≈ 0.4) by fitting a power-law model to the two spectra. To explain ∆α, we decomposed the recovered dust map into two gas phases: dust associated with neutral atomic hydrogen, and dust associated with molecular hydrogen. We provide a clear pathway to mapping the Galactic interstellar reddening over intermediate and high Galactic latitudes.