• SCUBA2_FCFNEFD

SCUBA2_FCFNEFD

Description

A simple PICARD recipe to calculate fluxes, FCFs and NEFDs from one or more given sources. The results are written to a log file called log.fcfnefd if desired.

The images are cropped to the given size (as specified in the FITS headers or via the MAP_HEIGHT and MAP_WIDTH recipe parameters) before having the background fitted and removed. The FCFs are calculated from these cropped, background-subtracted images. The source flux and image-plane noise are derived from aperture photometry on these images. NEFDs are calculated using the original input images (calibrated using either standard FCFs or those derived in the recipe, depending on USEFCF).

The FCF calculation requires uncalibrated data and thus must be performed first. However, note that the NEFD calculation must be carried out using the original input data (as background subtraction affects the variance).

By default this recipe only works on known calibration sources. However, the user may specify the source flux at 850 and/or 450 um by using recipe parameters called FLUX_850 and FLUX_450 respectively. The fluxes for different sources may be specified by appending the target name (in upper case with spaces removed), e.g. FLUX_850.HLTAU.

A log file is written containing a variety of information about the data and the values calculated (unless LOGFILE = 0).

Notes

The input data must have units of pW. If the units are anything else the recipe assumes the data are already calibrated, and subsequent processing will probably fail in undesireable ways.

Map height and width must be at least twice the aperture diameter.

If run on multiple sources and fluxes are given in the parameter file, warnings will be issued about unsupported parameters. These warnings may safely be ignored as they relate to the recipe parameters specifying the fluxes for the sources not being processed by the current pass through the recipe.

Peak and total fluxes may be given using the FLUX_850 and FLUX_450 parameters, specified as a comma-separated pair in the form peak,total (e.g. FLUX_850=2,3).

Available recipe parameters

• ANNULUS_INNER
  • scale factor (in terms of aperture radius) for inner radius of annulus used for background estimate (default is 1.25)
• ANNULUS_OUTER
  • scale factor for outer radius of annulus used for background estimate (default is 2)
• APERTURE_RADIUS
  • radius of aperture (in arcsec) for masking out source (otherwise 30 arcsec)
• AUTOPHOTOM

  • use KAPPA autophotom for aperture photometry

• BACKGROUND_FITMETHOD

  • the method for fitting the background, either fitsurface (default) or findback but may also be none if the background removal is already satisfactory

• FINDBACK_BOX

  • size of box in pixels used by findback for smoothing the image

• FITSURFACE_FITTYPE

  • FITTYPE parameter for fitsurface: polynomial (default) or spline

• FITSURFACE_FITPAR

  • parameters for FITTYPE in fitsurface, up to 2 numbers corresponding to NXPAR/NYPAR for polynomial or KNOTS for spline fit

• FITSURFACE_KEEPSURFACE
  • A flag to denote whether or not to keep the fitted surface on disk. Useful for debugging purposes. Default is 0 (do not keep on disk)
• FLUX_450
  • Source flux density at 450 um in Jy. Source-specific values may be given by appending the source name in upper case with spaces removed. Peak and total fluxes may be given as a comma-separated pair.
• FLUX_850
  • Source flux density at 850 um in Jy. Source-specific values may be given by appending the source name in upper case with spaces removed. Peak and total fluxes may be given as a comma-separated pair.
• KEEPFILES

  • Flag to denote whether to keep files on disk. May be +1 (keep _crop, _back and _mf), 0 (keep nothing) or -1 (keep everything, default).

• LOGFILE
  • Flag to denote whether to write results to a log file at the end of processing - default is 1 (write a log file)
• MAP_WIDTH
  • map width in arcsec
• MAP_HEIGHT
  • map height in arcsec
• MASK_SOURCE
  • flag to mask out a circular region on the source before fitting a background (1 = mask out source; 0 = do not mask out source - the default)
• USEFCF
  • Flag to denote whether to calibrate the data using the FCFs derived in this recipe (1) or use standard FCFs (0). Standard FCFs will be used if not specified.