The BINGO project

V. Further steps in component separation and bispectrum analysis

¹ Instituto de Física, Universidade de São Paulo, 05315-970 São Paulo, Brazil
² Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
³ Instituto Nacional de Pesquisas Espaciais – INPE, Divisão de Astrofísica, Av. dos Astronautas, 1758, 12227-010 São José dos Campos, SP, Brazil
⁴ Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
⁵ Center for Gravitation and Cosmology, College of Physical Science and Technology, Yangzhou University, Yangzhou 225009, PR China
⁶ Laboratoire Astroparticule et Cosmologie (APC), CNRS/IN2P3, Université Paris Diderot, 75205 Paris Cedex 13, France
⁷ IRFU, CEA, Université Paris Saclay, 91191 Gif-sur-Yvette, France
⁸ Department of Astronomy, School of Physical Sciences, University of Science and Technology of China, Hefei, Anhui 230026, PR China
⁹ Technische Universität München, Physik-Department T70, James-Franck-Stra β e 1, 85748 Garching, Germany
¹⁰ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild Str. 1, 85741 Garching, Germany
¹¹ Unidade Acadêmica de Física, Universidade Federal de Campina Grande, R. Aprígio Veloso, 58429-900 Bodocongó, Campina Grande – PB, Brazil
¹² Instituto de Física, Universidade de Brasília, Brasília, DF, Brazil
¹³ Centro de Gestão e Estudos Estratégicos – CGEE, SCS Quadra 9, Lote C, Torre C s/n Salas 401 – 405, 70308-200 Brasília, DF, Brazil
¹⁴ School of Aeronautics and Astronautics, Shanghai Jiao Tong University, Shanghai 200240, PR China
¹⁵ Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Canary Islands, Spain
¹⁶ Departamento de Astrofísica, Universidad de La Laguna (ULL), 38206 La Laguna, Tenerife, Spain
¹⁷ Center for Theoretical Physics of the Universe, Institute for Basic Science (IBS), Daejeon 34126, Korea

Received: 2 July 2021
Accepted: 1 November 2021

Abstract

Context. Observing the neutral hydrogen distribution across the Universe via redshifted 21 cm line intensity mapping constitutes a powerful probe for cosmology. However, the redshifted 21 cm signal is obscured by the foreground emission from our Galaxy and other extragalactic foregrounds. This paper addresses the capabilities of the BINGO survey to separate such signals.

Aims. We show that the BINGO instrumental, optical, and simulations setup is suitable for component separation, and that we have the appropriate tools to understand and control foreground residuals. Specifically, this paper looks in detail at the different residuals left over by foreground components, shows that a noise-corrected spectrum is unbiased, and shows that we understand the remaining systematic residuals by analyzing nonzero contributions to the three-point function.

Methods. We use the generalized needlet internal linear combination, which we apply to sky simulations of the BINGO experiment for each redshift bin of the survey. We use binned estimates of the bispectrum of the maps to assess foreground residuals left over after component separation in the final map.

Results. We present our recovery of the redshifted 21 cm signal from sky simulations of the BINGO experiment, including foreground components. We test the recovery of the 21 cm signal through the angular power spectrum at different redshifts, as well as the recovery of its non-Gaussian distribution through a bispectrum analysis. We find that non-Gaussianities from the original foreground maps can be removed down to, at least, the noise limit of the BINGO survey with such techniques.

Conclusions. Our component separation methodology allows us to subtract the foreground contamination in the BINGO channels down to levels below the cosmological signal and the noise, and to reconstruct the 21 cm power spectrum for different redshift bins without significant loss at multipoles 20 ≲ ℓ ≲ 500. Our bispectrum analysis yields strong tests of the level of the residual foreground contamination in the recovered 21 cm signal, thereby allowing us to both optimize and validate our component separation analysis.