Hello community!
I am trying to understand to which extent we can use LSST DP2 data to study intracluster light and I am trying to asses the impact of sky subtraction on measurements taken at large cluster-centric radii.
I would like to compare the sky estimation scale employed in LSST DP2 with those employed in previous surveys (256 × 256 pix for HSC PDR3 , 1024 × 1024 pixel box in HSC PDR2).
However, I have not been able to find the sky-estimation box size used for DP2. Does anyone know what size sky box is used to reduce DP2 deep coadds, or where this information is documented?
Just to clarify, 256x256 was the box size for small-scale subtraction of single visits. For the additional coadd background subtraction, the box size was 128x128 px. See 3.5 and 3.6 of Aihara et al. 2022.
Hi @ggolini, thanks for the question. Section 4.1.2 of RTN-115 describes what’s done at the visit level. This is the majority of the background subtraction, although there is a small removal of any remaining background from deep coadds as well. As Dan said, the coadd background is estimated in 128x128-pixel bins, with a 6th-order Akima spline interpolation. The documentation on background subtraction and image coaddition provides further information that may be helpful.
I’ll mark this post as the solution, but if further clarification is needed, feel free to unmark it and let us know.
After reading a bit of RTN-115, I have a related question: Is catalog-level sky background information available somewhere? Alternatively, is it possible to obtain survey property map sky background information at a higher HEALPix resolution (~CCD scale rather than the current maximum of ~pointing scale)? Thanks.