Deblending creating a lot of children

Hi all,

I have running some HSC data through LSSTstack, and making deep coadds across a sizeable piece of the sky. I noticed that running multiband takes a long time, on the oder of ~12 hours for a 0.5x0.5 deg sky tile, when running on 16 cores. Digging through the logs, the thing that stands out to me is the large number of children made when doing the deblending.

For reference, I am in fact only using one band (HSC-g) and stacking together 6 images in my example tile. They are all images with decent SNR, and astrometric calibration looks good. I blinked together the psfMatch warped images coming out of the coaddDriver run, and the sources look well centered in the blink of my 6 inputs. I am running Multiband and Coadd with default parameters.

At the moment, for this tile the results of he deblending are as follows:

Deblender results: of 47872 parent sources, 47772 were deblended, creating 68552 children, for a total of 116424 sources

This is pretty common across the test tiles I have run so far (completley different input images, obsdate and location of the sky).

This just seems strange to me, as it decides to deblend almost all the sources to create children, and the vast bulk of those have 1 child. Looking through the output forcedSrc, the rough average separation between the parent and deblended sources is about 0.02 arcsec, which is obviously well within the PSF.

I am wondering what the deblender is doing here, and if there is some way I can stop it from trying to deblend on such small scales.

I looked through the config files, but cannot find any parameter that can be used to e.g. tweak the scale/smoothing for deblending.

Detection is done before deblending, based on the number of peaks detected in each footprint. By default the deblender still runs on isolated sources, but if you want to skip them then set ScarletDeblendTask.processSingles=False and it won’t create duplicate records for the isolated parents, which is probably what you want.

This is perfect. Thanks!