The BINGO project

Abstract

Context. Observing the neutral hydrogen (Hi ) distribution across the Universe via redshifted 21cm line intensity mapping (IM) constitutes a powerful probe for cosmology. However, the redshifted 21cm 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 (GNILC), 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 21cm signal from sky simulations of the BINGO experiment, including foreground components. We test the recovery of the 21cm 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 21cm power spectrum for different redshift bins without significant loss at multipoles 20 500. Our bispectrum analysis yields strong tests of the level of the residual foreground contamination in the recovered 21cm signal, thereby allowing us to both optimize and validate our component separation analysis.

The Dark Sector Cosmology

“…Different techniques exploring different characteristics about foregrounds or about 21cm signal are available or under development to disentangle the signals. As an example we cite GNILC [40][41][42] and GMCA 43 that are also used in case of the CMB. 44 Other lines and atoms or molecules can also be used in IM such as CO(1-0) b , CO(2-1), CO(3-2) among others.…”

“…However, in order to see this fluctuation, the component separation must be as accurate as possible, such that contamination and errors in the data do not suppress fluctuations. In addition to foregrounds contamination, that is about a thousand times stronger than 21cm signal, there are contaminations such as polarization leakage, 43 1/f noise, 48 temperature system, Radio Frequency Interference (RFI), among others, that are smaller than foregrounds, but also very important contaminations that need to be precisely understood for the pipeline construction 42 and must be properly extracted.…”

The BINGO Project IV: Simulations for mission performance assessment and preliminary component separation steps

“…The GNILC method is also investigated in the BINGO paper V (Fornazier et al 2021) with contaminants generated from the PSM code. In this paper, the efficiency of GNILC in reconstructing Hi plus thermal noise maps in the presence of contaminants (already described in this work) is analyzed in respect of how the change of 1/ f parameters, number of feed horns and observation time influence this process.…”

“…5) and is good for frequencies 2.3 GHz. Our choice here differs from companion paper V (Fornazier et al 2021), who use the PSM synchrotron sky with the synchrotron spectral index distribution produced by Miville-Deschênes et al (2008).…”

“…This is the fourth (IV) of a series of papers describing the BINGO project. The theoretical and instrumental projects are in papers I and II (Abdalla et al 2021a;Wuensche et al 2021), the optical design in paper III (Abdalla et al 2021b), the component separation and correlations in paper V (Fornazier et al 2021), the simulations for a mock 21-cm catalog are described in paper VI (Zhang et al 2021) and the cosmological forecasts for BINGO in paper VII (Costa et al 2021).…”