Should we use per-object templates for bright objects in concert with full-image templates for image subtraction and DIA source identification?
The motivation is to ensure that bright objects in the template are created from combinations of consistent PSFs (i.e., not bad columns, saturated spikes, etc.). Getting the convolution wrong in the wings of the PSFs around bright objects will lead to significant numbers of false detection.
- Use a “standard” good-PSF coadd template for the subtractions.
- Then subtract these regions around bright objects with per-object templates for those bright objects.
- Generate a DIA source detection and measure based on the subtraction in Step 1 but masking regions around bright objects, and then add in the detections from the objects from Step 2.
- Simply masking objects brighter than, e.g., r< 17mag is reasonable. I’m thinking more of the next two magnitudes.
- This presumes that we’re really good at BF corrections, but that assumptions is necessary for the baseline as well.
- I dislike having sharp boundaries in detection, but we may implicitly have that anyway in templates due to different effective numbers of pixels contributing to each pixel in the template, and a different mix of images over the size of patch.
- We may naturally transition to such a regime. In the first 6 months we won’t have gaps through most bright objects. As we accumulate more images, the chance of a masked column/region being overlaid on to a bright object approach unity. At this point it may be worth implementing this proposed (semi-crazy) scheme.