A Decade of SCUBA-2: A Comprehensive Guide to Calibrating 450 $\mu$m and 850 $\mu$m Continuum Data at the JCMT

TL;DR

This paper provides a comprehensive calibration guide for SCUBA-2 at 450 and 850 micrometers, including updated atmospheric corrections, flux conversion factors, and calibration source fluxes, based on a decade of observations.

Contribution

It offers the first extensive recalibration of SCUBA-2 data, improving flux accuracy and stability assessments for all observations since 2011.

Findings

Total-flux uncertainty at 450μm is 14% during stable night hours.

Total-flux uncertainty at 850μm is 6% during stable night hours.

Updated calibration parameters enhance data reliability for SCUBA-2 observations.

Abstract

The Submillimetre Common User Bolometer Array 2 (SCUBA-2) is the James Clerk Maxwell Telescope's continuum imager, operating simultaneously at 450 and 850~$\mu$m. SCUBA-2 was commissioned in 2009--2011 and since that time, regular observations of point-like standard sources have been performed whenever the instrument is in use. Expanding the calibrator observation sample by an order of magnitude compared to previous work, in this paper we derive updated opacity relations at each wavelength for a new atmospheric-extinction correction, analyze the Flux-Conversion Factors (FCFs) used to convert instrumental units to physical flux units as a function of date and observation time, present information on the beam profiles for each wavelength, and update secondary-calibrator source fluxes. Between 07:00 and 17:00 UTC, the portion of the night that is most stable to temperature gradients that cause dish deformation, the total-flux uncertainty and the peak-flux uncertainty measured at 450~$\mu$m are found to be 14\% and 17\%, respectively. Measured at 850~$\mu$m, the total-flux and peak-flux uncertainties are 6\%, and 7\%, respectively. The analysis presented in this work is applicable to all SCUBA-2 projects observed since 2011.