Characterization of the MALT90 Survey and the Mopra Telescope at 90 GHz

TL;DR

This paper evaluates the MALT90 survey and Mopra telescope at 90 GHz, focusing on pointing accuracy, flux variability, and calibration improvements, providing essential insights for precise astronomical observations.

Contribution

It offers a detailed characterization of the MALT90 survey and Mopra telescope, including pointing reliability and flux calibration corrections at 90 GHz.

Findings

Pointing uncertainty estimated at 8 arcseconds.

Flux scatter reduced from 12-25% to 10-17% after corrections.

No intrinsic variability found in source G300.968+01.145.

Abstract

We characterize the Millimeter Astronomy Legacy Team 90 GHz (MALT90) Survey and the Mopra telescope at 90 GHz. We combine repeated position-switched observations of the source G300.968+01.145 with a map of the same source in order to estimate the pointing reliability of the position-switched observations and, by extension, the MALT90 survey; we estimate our pointing uncertainty to be 8 arcseconds. We model the two strongest sources of systematic gain variability as functions of elevation and time-of-day and quantify the remaining absolute flux uncertainty. Corrections based on these two variables reduce the scatter in repeated observations from 12-25% down to 10-17%. We find no evidence for intrinsic source variability in G300.968+01.145. For certain applications, the corrections described herein will be integral for improving the absolute flux calibration of MALT90 maps and other observations using the Mopra telescope at 90 GHz.