Exploring Cosmic History and Origin (ECHO), popularly known as ‘CMB-Bha¯¯¯rat’, is a space mission that has been proposed to the Indian Space Research Organisation for the scientific exploitation of the cosmic microwave background (CMB) at the next level of precision and accuracy. The quest for the CMB polarization B-mode signals, generated by inflationary gravitational waves in the very early universe, is one of the key scientific goals of its experimental design. This work studies the potential of the proposed ECHO instrumental configuration to detect the target tensor-to-scalar ratio r ∼ 10−3 at 3σ significance level, which covers the predictions of a large class of inflationary models. We investigate the performance of two different component separation pipelines, NILC and Commander, for the measurement of r in the presence of different physically motivated models of astrophysical foregrounds. For a simplistic foreground model (only polarized dust and synchrotron), both component separation pipelines can achieve the desired sensitivity of ECHO, i.e. σ(r = 0) ∼ (0.4–0.7) × 10−3. NILC performs better than Commander in terms of bias on recovered r for complex spectral models (power law and curved power law) of the synchrotron emission and complex dust models (dust decorrelation). Assuming 84 per cent delensing, we can achieve an improvement of σ(r = 0) by approximately 50 per cent as compared to the results obtained for the same configuration without any lensing correction. © 2022 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society.
DA acknowledges the University Grants Commission India for providing financial support as Senior Research Fellow. This work was supported by Science and Engineering Research Board, Department of Science and Technology, Govt. of India, grant number SERB/ECR/2018/000826. All the computation using the Commander code in this paper is done on the Pegasus cluster11 at IUCAA. The results in this paper have been derived using the HEALPIX package. DA acknowledges Prof. Hans Kristian Eriksen and Dr. Ranajoy Banerji for helping to install Commander and preparing the parameter files. DA also acknowledges Dr. Shabbir Shaikh for useful discussion. AS acknowledges the use of Padmanabha cluster12 at IISER-TVM for her work. AR acknowledges support from the ERC Consolidator Grant CMBSPEC (No. 725456) as part of the European Union’s Horizon 2020 research and innovation programme.
With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.