As of DM-15104 deblending is no longer performed by the MeasureMergedCoaddSourcesTask but instead is executed in the DeblendCoaddSourcesTask, which must be run before MeasureMergedCoaddSourcesTask to generate a catalog of deblended sources.
The new task can (optionally) create two new catalogs: deblendedModels, which are the scarlet models for each source and deblendedFlux, which are the flux conserved models created by using the scarlet models to reweight the flux in the input image. To export the scarlet models set DeblendCoaddSourcesTask.multibandDeblend.config.saveTemplates=True and to export the flux conserved models use DeblendCoaddSourcesTask.multibandDeblend.config.conserveFlux=True. However, the default deblender is still the HSC-SDSS single band deblender and not scarlet, so by default only the deblendedFlux catalog is generated.
MeasureMultibandCoaddSourcesTask can only run measurements on one catalog at a time, so when using the command line task the parameter MeasureMultibandCoaddSourcesTask.config.inputCatalog tells the task which dataset to use (“deblendedFlux”, “deblendedModel”, or “mergeDet” to use the merged catalog with no deblending).