Hydrogen intensity mapping with MeerKAT: Preserving cosmological signal by optimising contaminant separation

Year: 2025

Type: article

Abstract: Removing contaminants is a delicate, yet crucial step in neutral hydrogen (H I) intensity mapping and often considered the technique’s greatest challenge. Here, we address this challenge by analysing H I intensity maps of about 100 deg2 at redshift z ≈ 0.4 collected by the MeerKAT radio telescope, an SKA Observatory (SKAO) precursor, with a combined 10.5-hour observation. Using unsupervised statistical methods, we removed the contaminating foreground emission and systematically tested, step-by-step, some common pre-processing choices to facilitate the cleaning process. We also introduced and tested a novel multiscale approach: the data were redundantly decomposed into subsets referring to different spatial scales (large and small), where the cleaning procedure was performed independently. We confirm the detection of the H I cosmological signal in cross-correlation with an ancillary galactic data set, without the need to correct for signal loss. In the best set-up we achieved, we were able to constrain the H I distribution through the combination of its cosmic abundance (ΩH I) and linear clustering bias (bH I) up to a cross-correlation coefficient (r). We measured ΩH IbH Ir = [0.93 ± 0.17] × 10−3 with a ≈6σ confidence, which is independent of scale cuts at both edges of the probed scale range (0.04 ≲ k ≲ 0.3 h Mpc−1), corroborating its robustness. Our new pipeline has successfully found an optimal compromise in separating contaminants without incurring a catastrophic signal loss. This development instills an added degree of confidence in the outstanding science we can deliver with MeerKAT on the path towards H I intensity mapping surveys with the full SKAO.

Source: Springer Link (Chiba Institute of Technology)

DOI: 10.1051/0004-6361/202453461/pdf

Authors: I. P. Carucci, J. L. Bernal, S. Cunnington, M. G. Santos, J. Wang, J. Fonseca, K. Grainge, M. O. Irfan, Y. Li, A. Pourtsidou, M. Spinelli, L. Wolz

Institutions: Trieste Astronomical Observatory, Institute for Fundamental Physics of the Universe, National Institute for Astrophysics, Instituto de Física de Cantabria, University of Manchester, University of the Western Cape, Chinese Academy of Sciences, Shanghai Astronomical Observatory, Universidade do Porto, Institute of Astrophysics and Space Sciences, Centro de Astrofísica da Universidade do Porto, University of Cambridge, Northeastern University, Royal Observatory, University of Edinburgh, Lagrange Laboratory, Observatoire de la Côte d’Azur

Language: English

Topic: Radio Astronomy Observations and Technology

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: green

Funders: Dipartimenti di Eccellenza, European Commission, National Research Foundation, National Natural Science Foundation of China, Fundação para a Ciência e a Tecnologia, Agencia Estatal de Investigación

OpenAlex ID: W7111412819