Measurement of 21 cm brightness fluctuations at z ~ 0.8 in cross-correlation

TL;DR

This study measures 21 cm brightness fluctuations at redshift ~0.8 by cross-correlating intensity maps from the Green Bank Telescope with galaxy data from WiggleZ, providing the most precise constraint on neutral hydrogen fluctuations at this epoch.

Contribution

It presents the first precise measurement of neutral hydrogen density fluctuations at z ~ 0.8 using cross-correlation techniques, extending previous work in this redshift range.

Findings

Constrained Omega_HI b_HI r = [0.43 ± 0.07 (stat.) ± 0.04 (sys.)] x 10^-3.

Achieved the most precise measurement of neutral hydrogen fluctuations at z ~ 0.8.

Improved the range of scales and precision over previous 21 cm cross-correlation studies.

Abstract

In this letter, 21 cm intensity maps acquired at the Green Bank Telescope are cross-correlated with large-scale structure traced by galaxies in the WiggleZ Dark Energy Survey. The data span the redshift range 0.6 < z < 1 over two fields totaling ~41 deg. sq. and 190 hours of radio integration time. The cross-correlation constrains Omega_HI b_HI r = [0.43 \pm 0.07 (stat.) \pm 0.04(sys.)] x 10^-3, where Omega_HI is the neutral hydrogen HI fraction, r is the galaxy-hydrogen correlation coefficient, and b_HI is the HI bias parameter. This is the most precise constraint on neutral hydrogen density fluctuations in a challenging redshift range. Our measurement improves the previous 21 cm cross-correlation at z ~ 0.8 both in its precision and in the range of scales probed.