Spectral-line Observations Using a Phased Array Feed on the Parkes Telescope

TL;DR

This paper demonstrates the use of a phased array feed on the Parkes telescope to improve spectral-line observations, showing enhanced suppression of standing waves, successful detection of HI signals, and setting limits on positronium emission.

Contribution

First application of a phased array feed on the Parkes telescope showing improved standing wave suppression and successful HI observations across multiple redshifts.

Findings

PAF suppresses standing waves by a factor of ~10

Detected HI signals at specific redshifts in GAMA G23 field

Set upper limit on positronium recombination line emission

Abstract

We present first results from pilot observations using a phased array feed (PAF) mounted on the Parkes 64-m radio telescope. The observations presented here cover a frequency range from 1150 to 1480 MHz and are used to show the ability of PAFs to suppress standing wave problems by a factor of $\sim10$ which afflict normal feeds. We also compare our results with previous HIPASS observations and with previous HI images of the Large Magellanic Cloud. Drift scan observations of the GAMA G23 field resulted in direct HI detections at $z=0.0043$ and $z=0.0055$ of HIPASS galaxies J2242-30 and J2309-30. Our new measurements generally agree with archival data in spectral shape and flux density, with small differences being due to differing beam patterns. We also detect signal in the stacked HI data of 1094 individually undetected galaxies in the GAMA G23 field in the redshift range $0.05 \leq z \leq 0.075$. Finally, we use the low standing wave ripple and wide bandwidth of the PAF to set a $3\sigma$ upper limit to any positronium recombination line emission from the Galactic Centre of $<0.09$ K, corresponding to a recombination rate of $<3.0\times10^{45}\,\mathrm{s}^{-1}$.