Demonstration of hybrid foreground removal on CHIME data
The main challenge of 21-cm cosmology experiments is astrophysical foregrounds that are difficult to separate from the signal due to telescope systematics. An earlier study has shown that foreground residuals induced by antenna gain errors can be estimated and subtracted using the hybrid foreground residual subtraction (HyFoReS) technique, which relies on cross-correlating linearly filtered data. In this paper, we apply a similar technique to the CHIME stacking analysis to subtract beam-induced foreground contamination. Using a linear high-pass delay filter for foreground suppression, the CHIME collaboration reported a $11.1\ensuremath{\sigma}$ detection in the 21-cm signal stacked on eBOSS quasar locations, despite foreground residual contamination mainly due to the instrument chromatic transfer function. Following the HyFoReS formalism, we cross-correlate the foreground-dominated data at low delay with the contaminated signal at high delay to estimate residual foregrounds and subtract them from the signal. We find that HyFoReS can improve the signal-to-noise ratio of the stacked 21-cm signal by 10%--20% after the delay foreground filter, although some of the improvement can also be achieved with an alternative flagging technique. We have shown that it is possible to use HyFoReS to reduce beam-induced foreground contamination, benefiting the analysis of the HI auto power spectrum with CHIME and enabling the recovery of large-scale modes.
Authors
- Dallas Wulf (ORCID: https://orcid.org/0000-0001-7314-9496)
- Kiyoshi W. Masui (ORCID: https://orcid.org/0000-0002-4279-6946)
- M. Halpern (ORCID: https://orcid.org/0000-0002-1760-0868)
- Alex Reda (ORCID: https://orcid.org/0000-0001-6967-7253)
- Arnab Chakraborty (ORCID: https://orcid.org/0000-0002-7758-9859)
- Pranav Sanghavi (ORCID: https://orcid.org/0000-0001-5504-229X)
- Simon Foreman (ORCID: https://orcid.org/0000-0002-0190-2271)
- Laura Newburgh (ORCID: https://orcid.org/0000-0002-7333-5552)
- Seth R. Siegel (ORCID: https://orcid.org/0000-0003-2631-6217)
- Haochen Wang (ORCID: https://orcid.org/0000-0002-1491-3738)
- M. Dobbs (ORCID: https://orcid.org/0000-0001-7166-6422)
- Joshua MacEachern (ORCID: https://orcid.org/0000-0001-8064-6116)
- Kevin Bandura (ORCID: https://orcid.org/0000-0003-3772-2798)
- Sourabh Paul (ORCID: https://orcid.org/0000-0002-8671-2177)
- Liam Gray (ORCID: https://orcid.org/0000-0003-3986-954X)
- Juan Mena-Parra
- Albin Joseph (ORCID: https://orcid.org/0000-0003-4179-4073)
- Kyle Miller (ORCID: https://orcid.org/0000-0002-7001-6660)
Institutions
- West Virginia University (US)
- University of British Columbia (CA)
- Lane College (US)
- Perimeter Institute (CA)
- University of Toronto (CA)
- University of Manchester (GB)
- Yale University (US)
- Kavli Institute for Particle Astrophysics and Cosmology (US)
- Canadian Institute for Theoretical Astrophysics (CA)
- McGill University (CA)
- Arizona State University (US)
- Massachusetts Institute of Technology (US)
Publication Details
- Journal
- Physical review. D/Physical review. D.
- Published
- 2025-05-23
- DOI
- https://doi.org/10.1103/physrevd.111.103531
- Citations
- 4
- Primary Topic
- Astrophysics and Cosmic Phenomena
- Type
- article
- Field-Weighted Citation Impact
- 7.48
Funders
- National Science Foundation
- U.S. Department of Energy
- Alfred P. Sloan Foundation
- Canadian Institute for Advanced Research
- University of Utah
- Dunlap Institute for Astronomy and Astrophysics, University of Toronto
- McGill University
- Government of Canada
- Canada Foundation for Innovation
- Canada Research Chairs
- University of Toronto
- University of British Columbia
- Institut Périmètre de physique théorique
- Office of Science
- Center for High Performance Computing
- Natural Sciences and Engineering Research Council of Canada
- Fonds de recherche du Québec – Nature et technologies
- Ontario Ministry of Research and Innovation