Automatically adding fake sources to real data, part 2

In a previous entry, I described how to go use the new ORAC-DR recipe REDUCE_SCAN_FAKEMAP to automatically add fake sources to the raw time series in order to get a handle on the transfer function of the map-maker. That's all very well, but how about starting with something simpler, such as a Gaussian? Now you can add a Gaussian of given amplitude and FWHM without first creating an image to feed in to the pipeline. As before, the Gaussian properties are defined using recipe parameters:

[REDUCE_SCAN_FAKEMAP]
FAKEMAP_FWHM = 15
FAKEMAP_SCALE = 0.5
FAKEMAP_OFFSET = dx,dy

The FWHM is in arcsec and is the only mandatory parameter (the SCALE and OFFSET are optional). In this case, the FAKEMAP_SCALE parameter is the amplitude of the Gaussian in Jy/beam. The Gaussian can be positioned anywhere in the map by giving an offset (RA, Dec in arcsec).

The pipeline can help you out further by using a couple of useful defaults. If the world "beam" is given as the FWHM, then the pipeline will use the default beam size appropriate for the current wavelength (14" at 850 um, 8" at 450 um). If the amplitude is not specified then (somewhat arbitrary) defaults of 1 and 4 Jy/beam are assumed (at 850 and 450 um respectively).

Note that the FWHM must be greater than half the pixel scale (the pipeline will set it to that value if the given value is less), but in principle there is no upper limit. In practice the upper limit is defined by the array footprint (about 2.5 arcmin for S2SRO data): anything much larger than that will be removed by makemap as part of fitting the common mode.

As usual, update your Starlink installation (with rsync) to try it out.