Detection of the Cosmological 21 cm Auto Power Spectrum with CHIME at z > 1

by Dr Arnab Chakraborty (Trottier Space Institute, McGill University)

Friday 6 Feb 2026, 14:30 → 15:30 Asia/Kolkata

A 304 and on Zoom

The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a drift-scan radio interferometer located at the Dominion Radio Astrophysical Observatory (DRAO) in Penticton, British Columbia, Canada. CHIME, operating between 400 and 800 MHz, will map the redshifted 21-cm emission of neutral hydrogen between redshifts z = 0.8 − 2.5 across the northern sky. Measuring this cosmological signal is exceptionally challenging, as it is dwarfed by astrophysical foregrounds that are 4-5 orders of magnitude brighter, compounded by instrumental systematics and terrestrial radio frequency interference (RFI).  I will discuss key advances in data processing developed to address these challenges, including new methods for RFI excision, time-series foreground filtering, and bandpass calibration that significantly reduce systematics associated with RFI and foreground leakage.  These improvements have enabled a high signal-to-noise detection of the 21-cm power spectrum at redshift ~1.16 for k > 0.3 h Mpc^{-1}. Extensive validation tests confirm the cosmological origin of the detected signal, with results showing consistency between the auto-power spectrum and cross-correlations with eBOSS quasars. I will present these measurements of the auto power spectrum using CHIME data and discuss the resulting constraints on the abundance of neutral hydrogen at these redshifts.