H i constraints from the cross-correlation of eBOSS galaxies and Green Bank Telescope intensity maps

Laura Wolz, Alkistis Pourtsidou, Kiyoshi W. Masui, Tzu Ching Chang, Julian E. Bautista, Eva Maria Müller, Santiago Avila, David Bacon, Will J. Percival, Steven Cunnington, Chris Anderson, Xuelei Chen, Jean Paul Kneib, Yi Chao Li, Yu Wei Liao, Ue Li Pen, Jeffrey B. Peterson, Graziano Rossi, Donald P. Schneider, Jaswant YadavGong Bo Zhao

Research output: Contribution to journalArticlepeer-review

48 Scopus citations


We present the joint analysis of Neutral Hydrogen (H i) Intensity Mapping observations with three galaxy samples: the Luminous Red Galaxy (LRG) and Emission Line Galaxy (ELG) samples from the eBOSS survey, and the WiggleZ Dark Energy Survey sample. The H i intensity maps are Green Bank Telescope observations of the redshifted 21 cm emission on 100, deg2 covering the redshift range 0.6 < z < 1.0. We process the data by separating and removing the foregrounds present in the radio frequencies with FastI ICA. We verify the quality of the foreground separation with mock realizations, and construct a transfer function to correct for the effects of foreground removal on the H i signal. We cross-correlate the cleaned H i data with the galaxy samples and study the overall amplitude as well as the scale dependence of the power spectrum. We also qualitatively compare our findings with the predictions by a semianalytical galaxy evolution simulation. The cross-correlations constrain the quantity Ω HI b HI r HI, opt at an effective scale keff, where Ω HI is the HI density fraction, bHI is the HI bias, and r HI, opt the galaxy-hydrogen correlation coefficient, whicHIs dependent on the HI content of the optical galaxy sample. At k eff=0.31 \, h, Mpc-1 we find Ω HI b HI r HI Wig = [0.58 ± 0.09 (stat) ± 0.05 (sys)] × 10-3 for GBT-WiggleZ, Ω HI b HI r HI, ELG = [0.40 ± 0.09 (stat) ± 0.04 (sys)] × 10-3 for GBT-ELG, and Ω HI b HI r HI,LRG = [0.35 ± 0.08 (stat) ± 0.03 (sys)] × 10-3 for GBT-LRG, at z 0.8. We also report results at k eff=0.24 and k eff=0.48 h Mpc-1. With little information on HI parameters beyond our local Universe, these are amongst the most precise constraints on neutral hydrogen density fluctuations in an underexplored redshift range.

Original languageEnglish (US)
Pages (from-to)3495-3511
Number of pages17
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
StatePublished - Mar 1 2022

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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