ICTS:31366

Video URL

Progress towards measuring HI auto-power spectrum with CHIME

Progress towards measuring HI auto-power spectrum with CHIME

(2025). Progress towards measuring HI auto-power spectrum with CHIME. SciVideos. https://youtu.be/d88vaHAK6Cw

Progress towards measuring HI auto-power spectrum with CHIME. SciVideos, Apr. 07, 2025, https://youtu.be/d88vaHAK6Cw 

          @misc{ scivideos_ICTS:31366,
            doi = {},
            url = {https://youtu.be/d88vaHAK6Cw},
            author = {},
            keywords = {},
            language = {en},
            title = {Progress towards measuring HI auto-power spectrum with CHIME},
            publisher = {},
            year = {2025},
            month = {apr},
            note = {ICTS:31366 see, \url{https://scivideos.org/index.php/icts-tifr/31366}}
          }
Arnab Chakraborty
Talk numberICTS:31366
Source RepositoryICTS-TIFR
Collection

Abstract

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. The 21cm line is a tracer of the large-scale structure of matter, whose statistics encode a well-understood standard ruler, the baryon acoustic oscillation scale. By detecting and tracking the evolution of this scale with redshift, CHIME aims to constrain the expansion history of the Universe over this crucial redshift epoch when the overall energy density of the Universe is expected to have become dominated by dark energy.

However, measuring this cosmological signal is challenging due to bright astrophysical foregrounds, which are about 4-5 orders of magnitude brighter than the cosmological HI signal.

In principle, these two signals can be separated due to their different spectral features, in which, the foreground signal is smooth in frequency, whereas the cosmological signal has spectral structure. However, this separation requires an instrument calibration at the sub-percent level accuracy. Recently, the CHIME collaboration reported the detection of cosmological 21 cm emission from a large-scale structure between redshift 0.78 and 1.43 in cross-correlation with eBOSS galaxy and quasar catalogs. In this cross-correlation measurement, a high-pass filter is applied to the frequency axis of each map pixel to remove foregrounds, which results in a measurement of the cosmological signal at the non-linear scales. I will discuss recent results in measuring the 21 cm signal in auto-correlation and some of the challenges that we have encountered. I will describe the improvements in the data processing and various data quality cuts required to measure the signal in auto-correlation. I will show the first results of the power spectrum using CHIME data.