Testing synchrotron models and frequency resolution in BINGO 21 cm simulated maps using GNILC

¹ Divisão de Astrofísica, Instituto Nacional de Pesquisas Espaciais – INPE, Av. dos Astronautas 1758, 12227-010 São José dos Campos, SP, Brazil
² Center for Gravitation and Cosmology, YangZhou University, Yangzhou 224009, PR China
e-mail: larissa@yzu.edu.cn
³ CNRS-UCB International Research Laboratory, Centre Pierre Binétruy, IRL2007, CPB-IN2P3, Berkeley, CA 94720, USA
⁴ Instituto de Física de Cantabria (CSIC-UC), Avenida de los Castros s/n, 39005 Santander, Spain
⁵ Instituto de Física, Universidade de São Paulo, R. do Matão, 1371 – Butantã, 05508-09 São Paulo, SP, Brazil
⁶ University College London, Gower Street, London WC1E 6BT, UK
⁷ Department of Physics and Electronics, Rhodes University, PO Box 94 Grahamstown 6140, South Africa
⁸ Department of Astronomy, School of Physical Sciences, University of Science and Technology of China, Hefei, Anhui 230026, PR China
⁹ CAS Key Laboratory for Research in Galaxies and Cosmology, University of Science and Technology of China, Hefei, Anhui 230026, PR China
¹⁰ School of Astronomy and Space Science, University of Science and Technology of China, Hefei, Anhui 230026, PR China
¹¹ Unidade Acadêmica de Física, Universidade Federal de Campina Grande, R. Aprígio Veloso, Bodocongó, 58429-900 Campina Grande, PB, Brazil
¹² Centro de Gestão e Estudos Estratégicos SCS Qd 9, Lote C, Torre C S/N Salas 401 a 405, 70308-200 Brasília, DF, Brazil
¹³ Instituto de Física, Universidade de Brasília, Campus Universitário Darcy Ribeiro, 70910-900 Brasília, DF, Brazil
¹⁴ School of Aeronautics and Astronautics, Shanghai Jiao Tong University, Shanghai 200240, PR China
¹⁵ Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030, PR China
¹⁶ Kavli Institute for the Physics and Mathematics of the Universe (KIPMU), University of Tokyo, 5-1-5 Kashiwa-no-Ha, Kashiwa Shi, Chiba, 277-8568 Kashiwa-shi, Japan
¹⁷ Technische Universität München, Physik-Department T70, James-Franck-Strasse 1, 85748 Garching, Germany
¹⁸ College of Physics, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, PR China

Received: 17 April 2022
Accepted: 22 November 2022

Abstract

Context. The 21 cm hydrogen line is arguably one of the most powerful probes with which to explore the Universe, from recombination to the present times. To recover it, it is essential to separate the cosmological signal from the much stronger foreground contributions at radio frequencies. The Baryon Acoustic Oscillations from Integrated Neutral Gas Observations (BINGO) radio telescope is designed to measure the 21 cm line and detect baryon acoustic oscillations (BAOs) using the intensity mapping (IM) technique.

Aims. This work analyses the performance of the Generalized Needlet Internal Linear Combination (GNILC) method when combined with a power spectrum debiasing procedure. This method was applied to a simulated BINGO mission, building upon previous work from the collaboration. It compares two different synchrotron emission models and different instrumental configurations and takes into account ancillary data in order to optimize both the removal of foreground emission and the recovery of the 21 cm signal across the full BINGO frequency band and to determine an optimal number of frequency (redshift) bands for the signal recovery.

Methods. We produced foreground emission maps using the Planck Sky Model (PSM) and generated cosmological HI emission maps using the Full-Sky Log-normal Astro-Fields simulation Kit (FLASK) package. We also created thermal noise maps according to the instrumental setup. We apply the GNILC method to the simulated sky maps to separate the HI plus thermal noise contribution and, through a debiasing procedure, recover an estimate of the noiseless 21 cm power spectrum.

Results. We find a near-optimal reconstruction of the HI signal using an 80-bin configuration, which resulted in a power-spectrum reconstruction average error over all frequencies of 3%. Furthermore, our tests show that GNILC is robust against different synchrotron emission models. Finally, adding an extra channel with C-Band All-Sky Survey (CBASS) foregrounds information, we reduced the estimation error of the 21 cm signal.

Conclusions. The optimization of our previous work, producing a configuration with an optimal number of channels for binning the data, significantly impacts decisions regarding BINGO hardware configuration before commissioning. We were able to recover the HI signal with good efficiency in the harmonic space, but have yet to investigate the effect of 1/f noise in the data, which will possibly impact the recovery of the HI signal. This issue will be addressed in forthcoming work.