An HI intensity mapping survey with a Phased Array Feed

TL;DR

This paper reports on a neutral hydrogen intensity mapping survey using a Phased Array Feed on the Parkes telescope, detecting cross-correlation signals and paving the way for improved measurements of cosmic HI density at redshifts up to one.

Contribution

It introduces a novel HI intensity mapping survey with a Phased Array Feed, including data processing techniques and initial detection of cross-correlation signals with optical data.

Findings

Detected cross-correlation between HI maps and WiggleZ data

Achieved mean amplitude of 1.32 ± 0.42 mK in the signal

Future upgrades expected to improve measurement accuracy

Abstract

We report results from a neutral hydrogen (HI) intensity mapping survey conducted with a Phased Array Feed (PAF) on the Parkes telescope. The survey was designed to cover ~ 380 deg^2 over the redshift range 0.3 < z < 1 (a volume of ~ 1.5 Gpc^3) in four fields covered by the WiggleZ Dark Energy Survey. The results presented here target a narrow redshift range of 0.73 < z < 0.78 where the effect of radio frequency interference (RFI) was less problematic. The data reduction and simulation pipeline is described, with an emphasis on flagging of RFI and correction for signal loss in the data reduction process, particularly due to the foreground subtraction methodology. A cross-correlation signal was detected between the HI intensity maps and the WiggleZ redshift data, with a mean amplitude of<{\Delta}T_b{\delta}_{opt}> = 1.32 \pm 0.42 mK (statistical errors only). A future Parkes cryogenic PAF is expected to detect the cross-correlation signal with higher accuracy than previously possible and allow measurement of the cosmic HI density at redshifts up to unity.