profoundDiscoSky: Per Discontinuity Region Sky Map

In asgr/ProFound: Photometry Tools

Per Discontinuity Region Sky Map

Description

This function allows the sky in an image to vary in a discontinuous manner between regions, as described by the disco discontinuity region map. The typical use case would be a CCD/CMOS sensor that has multichannel read out. This often creates extemely sharp features even within a single image that are not well captured for a smooth bicubic spline.

Usage

profoundDiscoSky(image, disco, sky_arg_list = NULL, roughpedestal = FALSE, mask = NULL,
  ...)

Arguments

image	Numeric matrix; required, the image we want to analyse.
disco	Integer matrix; required, the discontinuity region map. This should be numbered from 1:N for N regions, with no gaps. Regions should be contiguous, or weird things may happen.
sky_arg_list	List; a list of per discontinuity region profoundMakeSkyGrid arguments (see Examples). This allows fine control over difference regions of the image if required.
roughpedestal	Logical; should only a pedestal (based on the median of the sky/skyRMS map) be used for the sky/skyRMS? This is a good option if the image is known to contain a *very* large (many times the box size) galaxy that might otherwise be over subtracted by the initial rough sky map.
mask	Boolean matrix; optional, parts of the image to mask out (i.e. ignore), where 1 means mask out and 0 means use for analysis. If provided, this matrix *must* be the same dimensions as image.
...	Other global arguments to pass into profoundMakeSkyGrid.

Details

This function is not incorporated into the higher level profoundProFound function. In general it is only useful for extreme cases of big discontinuities within images due to different read out chips and/or artefacts created by image mosaicing (if this is not done optimally, you often see discrete jumps in the sky and skyRMS between regions.

Creting the disco discontinuity region map has to be done manually, but users should consider using the sky and skyRMS outputs of a standard run of profoundProFound for guidance.

Value

Produces a list of 2 matrices. The first (called sky) is a matrix of values for the absolute sky; the second (called skyRMS) is a matrix of values for the absolute sky RMS.

Author(s)

Aaron Robotham

See Also

profoundMakeSkyGrid

Examples

## Not run: 
image = Rfits_read_image(system.file("extdata", 'VIKING/mystery_VIKING_Z.fits',
  package="ProFound"))$imDat
profound = profoundProFound(image) #We want this for the object mask.

#Create toy disco region map:
disco = matrix(1L,356,356) #firstly set everything to region 1.
disco[,1:178] = 2L #half the region is flagged as region 2.

#First we run with just an object mask and take a look:
sky = profoundDiscoSky(image, disco=disco, objects=profound$objects_redo)
#The discontinuity is obvious along the horizontal.
magimage(sky$sky)

#Different box sizes for the different disco regions (default is 100 otherwise):
sky = profoundDiscoSky(image, disco=disco, sky_arg_list=list(list(box=50),list(box=25)),
  objects=profound$objects_redo)
magimage(sky$sky)

#Just using a pedestal:
sky = profoundDiscoSky(image, disco=disco, objects=profound$objects_redo,
  roughpedestal=TRUE)
magimage(sky$sky)
table(sky$sky) #just two different sky values for the two disco regions.

## End(Not run)

asgr/ProFound documentation built on Feb. 10, 2024, 9:04 p.m.