SCUBA-2: on-sky calibration using submillimetre standard sources

TL;DR

This paper details the calibration process of the SCUBA-2 submillimetre camera, including improved atmospheric models and flux calibration, achieving high accuracy and stability over several months, enabling reliable measurements of astronomical sources.

Contribution

The paper introduces improved calibration algorithms and atmospheric extinction models for SCUBA-2, resulting in highly accurate flux calibration at 850 and 450 microns.

Findings

Calibration accuracy better than 5% at 850 microns

Calibration accuracy better than 10% at 450 microns

Stable performance over several months

Abstract

SCUBA-2 is a 10000-bolometer submillimetre camera on the James Clerk Maxwell Telescope (JCMT). The instrument commissioning was completed in September 2011, and full science operations began in October 2011. To harness the full potential of this powerful new astronomical tool, the instrument calibration must be accurate and well understood. To this end, the algorithms for calculating the line-of-sight opacity have been improved, and the derived atmospheric extinction relationships at both wavebands of the SCUBA-2 instrument are presented. The results from over 500 primary and secondary calibrator observations have allowed accurate determination of the flux conversion factors (FCF) for the 850 and 450 micron arrays. Descriptions of the instrument beam-shape and photometry methods are presented. The calibration factors are well determined, with relative calibration accuracy better than 5 per cent at 850 microns and 10 per cent at 450 microns, reflecting the success of the derived opacity relations as well as the stability of the performance of the instrument over several months. The sample-size of the calibration observations and accurate FCFs have allowed the determination of the 850 and 450 micron fluxes of several well-known submillimetre sources, and these results are compared with previous measurements from SCUBA.