SCUBA-2 Calibrators

Primary Calibrators

Uranus and Mars are used as the primary calibrators for SCUBA-2. Calibrators for SCUBA-2 are observed with a DAISY pattern which is optimised for point-like and compact sources. When determining the standard FCF numbers the data were reduced using the SMURF routine makemap. The total flux for each calibrator was determined using a 60 arcsec diameter aperture, with the background level calculated between the diameters 90-120 arcsecs.

For further details, including a description of the derivation of the FCF, see Dempsey et al. MNRAS, 2013.
For instructions on applying the FCF see the SCUBA-2 data reduction cookbook (HTML), also available as a PDF version.

Fluxes

Starlink supplies a command line program FLUXES which can return the expected flux for each planet for any date specified. Several options are available including writing the data to a file, and returning the values today. Alternatively if you are at the telescope you can use the FLUXNOW program which defaults to the current date and time.

Secondary Calibrators

Source R.A. Dec. 850 µm 450 µm
  Peak flux (Jy/beam)    Integ. flux (Jy)    Peak flux (Jy/beam)    Integ. flux (Jy) 
CRL 618 04:42:53.67 +36:06:53.17 4.89 ± 0.24 5.0 ± 0.2 11.5 ± 1.4 12.1 ± 1.05
CRL 2688 21:02:18.27 +36:41:37.00 5.64 ± 0.27 6.13 ± 0.2 24.9 ± 2.9 29.1 ± 2.5
Arp 220 15:34:57.27 +23:30:10.48 0.79 ± 0.09 0.81 ± 0.07 5.2 ± 0.8 5.4 ± 0.7
HD 169142 18:24:29.78 -29:46:49.37 0.52 ± 0.03 0.58 ± 0.02 2.21 ± 0.25 2.78 ± 0.24
HD 135344B 15:15:48.44 -37:09:16.02 0.46 ± 0.03 0.53 ± 0.02 1.66 ± 0.27 3.30 ± 0.34
MWC 349 20:32:45.53 40:39:36.6 2.21 ± 0.11 2.19 ± 0.08 3.4 ± 0.26 3.2 ± 0.25
V883 Ori 05:38:19 -07:02:22 1.55 ± 0.09 2.0 ± 0.07 7.8 ± 1.0 11.0 ± 0.94
HL Tau 04:31:38.44 +18:13:57.65 2.32 ± 0.01 2.42 ± 0.08 8.3 ± 1.03 10.3 ± 0.86

For full details see Dempsey et al. (2013).

For historical reference, the calibration information for the original SCUBA can be found here.

SCUBA Calibration

Primary Calibrators

The primary sources used for calibration of SCUBA data are the planets Mars, Uranus and Neptune. The brightness of these sources varies with time – as the spatial separation between the Earth and each planet varies. In addition the brightness of Mars varies depending on the orientation of the planet with respect to both the Earth and the Sun.

Secondary Calibrators

For SCUBA data we point you to the SCUBA Data Reduction Cookbook, which contains a quick guide as well as further advice.

The primary flux calibration of SCUBA data is based on the planets Mars, Uranus and Neptune, but at some times of the night and year these may be unavailable. A (very) small set of ‘secondary’ calibrators has been collated from a variety of sources to use during these times, but these are few and far between and most of them are not ideal!

The values below were obtained for a new analysis of observations between April 1st 2000 and September 30th 2003, with the exception of the variable calibrators OH 231.8 and IRC+10216, for which the complete data sets have been used from 1997 – 2003. The values are all in agreement with our previous values, derived from (usually fewer) observations between 1997 and 2001. Wherever possible, only observations with 120″ chop throws have been used in this analysis. For the variable calibrators, use the links in the table below to see the updated curves.

For each source, two flux estimates are given at each wavelength. The first is the peak flux, in Jy/beam, which can be used for unresolved sources and also for photometry observations (see this note for guidance). The second is the integrated flux within a circular aperture with 20″ radius, in Jy/aperture, which should be used for resolved sources (see this paper by Jenness et al. for a more in-depth discussion on this issue).

 

  Calibrator R.A. Dec. 850 µm 450 µm
 Peak flux (Jy/beam)  Integ. flux (Jy/aper.)  Peak flux (Jy/beam)  Integ. flux (Jy/aper.)
HL Tau 04:31:38.4 +18:13:59 2.35 ± 0.08 2.36 ± 0.09 9.4 ± 1.3 10.4 ± 1.4
CRL 618 04:42:53.6 +36:06:53.7 4.6 ± 0.2 4.7 ± 0.12 10.9 ± 0.9 11.8 ± 0.6
OH 231.8 07:42:16.9 -14:42:49.1 Variable Variable Cannot be used Cannot be used
IRC 10216 09:47:57.4 +13:16:43.7 Variable Variable Cannot be used Cannot be used
16293-2422 16:32:22.9 -24:28:35.6 15.1 ± 0.8 22.9 ± 1.1 62.7 ± 9.4 169.6 ± 21.2
CRL 2688 21:02:18.8 +36:41:37.7 5.9 ± 0.2 6.4 ± 0.2 22.0 ± 2.7 29.7 ± 2.1

The previous version of this document supplied fluxes for OH 231.8 and IRC 10216 at 450 µm; however, later data does not support these numbers. The two sources are clearly variable at 850 µm and it is likely that they are at 450 µm also; the scatter in the data is too large to fit a curve.

Calibration has not been attempted at 350/750 micron, and very few 1350um data were available before the filter drum broke in 1999. However, numbers are still available upon request.

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