Photo's Deblender

Overview of Deblender

The photo deblender is based on the peaks found in each object. The basic idea is that we take the list of all peaks found within the parent, in any band (a peak need only appear in one band to be considered); each of these peaks is taken to define the centre of a possible child.

For each child, in each band we create a template, an approximate light distribution for the child (for a star, this template would be simply the PSF). We then assume that in each band

    parent = sum_i (weight_i template_i)
and solve for the weights. With these in hand we can then assign the flux associated with each child in each pixel according to the value of weight_i template_i, and our task is complete.

Note that, because the children are associated with the master list of peaks detected in any band, the resulting children are defined consistently in each band so it makes sense to (e.g.) ask questions about their colours.

Photo's Deblending Algorithm

Photo's deblender works by looking at the list of PEAKs in an OBJC, and treats each as the centre of a child. This list was produced by Measure Objects. The deblender proceeds as follows: At the end of this procedure, each child knows the values of all its pixels that lie within the OBJMASK defining the parent, and it is ready to be passed to Measure Objects.

Book Keeping for the Deblender

Once an object is deblended, it is represented as an OBJC as usual, but with a non-NULL children field which points at one of its children; in addition its OBJECT1_BLENDED bit is set, and nchild is one or more.

Each child has a non-NULL parent field which points to its parent, and may have a sibbs field too. It has its OBJECT1_CHILD bit set.