Implementation of Tidbinbilla 70-m On-The-Fly mapping and Hydrogen radio recombination line early results

TL;DR

This paper reports the implementation of on-the-fly spectral line mapping at Tidbinbilla 70-m, presenting new hydrogen recombination line maps and demonstrating efficiency gains for large and faint line observations.

Contribution

It introduces a new on-the-fly mapping technique at Tidbinbilla and provides initial results on hydrogen recombination lines in Orion A and Sagittarius A.

Findings

New H92α radio recombination line maps of Orion A and Sagittarius A.

On-the-fly mapping significantly improves efficiency for large bright line maps.

Potential for efficient mapping of faint lines like ammonia inversion lines.

Abstract

On-the-fly mapping of cm-wave spectral lines has been implemented at the the Tidbinbilla 70-m radio antenna. We describe the implementation and data reduction procedure and present new H92$\alpha$ radio recombination line maps towards Orion A and Sagittarius A. Comparison of the Orion~A map to previous observations suggests that the lines arise largely from gas with electron density of 100--200\,cm$^{-3}$. On-the-fly mapping is very efficient at generating large maps of bright lines (such as radio recombination lines), but will still yield strong efficiency gains for smaller maps of fainter lines, such as the ammonia inversion lines at the 1.3\,cm wavelength.