Improved upper limits on the 21-cm signal power spectrum of neutral hydrogen at $\boldsymbol{z \approx 9.1}$ from LOFAR

Mertens F. G.,Mevius M.,Koopmans L. V. E,Offringa A. R.,Mellema G.,Zaroubi S., Brentjens M. A.,Gan H.,Gehlot B. K.,Pandey V. N.,Sardarabadi A. M.,Vedantham H. K.,Yatawatta S.,Asad K. M. B.,Ciardi B.,Chapman E.,Gazagnes S.,Ghara R.,Ghosh A., Giri S. K.,Iliev I. T.,Jelić V., Kooistra R.,Mondal R.,Schaye J.,Silva M. B.

Monthly Notices of the Royal Astronomical Society（2020）

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摘要

A new upper limit on the 21 cm signal power spectrum at a redshift of z ≈ 9.1 is presented, based on 141 h of data obtained with the Low-Frequency Array (LOFAR). The analysis includes significant improvements in spectrally smooth gain-calibration, Gaussian Process Regression (GPR) foreground mitigation and optimally weighted power spectrum inference. Previously seen ‘excess power’ due to spectral ...

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methods: data analysis,techniques: interferometric,dark ages, reionization, first stars,cosmology: observations

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