DIA forced source#

Forced measurements in visit and difference images, at the coordinates of all DIA objects.

Schema: ForcedSourceOnDiaObject table

Access#

The DIA forced source table is accessible via the TAP and Butler services.

Recommended access service: TAP

TAP#

Citation: NSF-DOE Vera C. Rubin Observatory (2026); Legacy Survey of Space and Time Data Preview 2: ForcedSourceOnDiaObject searchable catalog https://doi.org/10.71929/rubin/3382536 [BibTeX]
Table name: ForcedSourceOnDiaObject
Columns: 26
Rows: 24,259,599,059

Butler#

Citation: NSF-DOE Vera C. Rubin Observatory (2026); Legacy Survey of Space and Time Data Preview 2: dia_object_forced_source dataset type https://doi.org/10.71929/rubin/3382535 [BibTeX]
Dataset type: (‘dia_object_forced_source’, {skymap, tract, patch}, ArrowAstropy)
Format: Parquet
Number of Butler datasets: 183,169

Forced sources are sharded by patch, not just tract, because in regions with many epochs the size of a full tract table becomes unwieldy.

Description#

“Forced” photometry means a measurement made at a fixed coordinate in an image, regardless of whether an above-threshold region was detected there in that particular image.

The DIA forced source table contains forced PSF flux photometry on both the visit (i.e., “direct” or “science”) and difference images at the coordinates of every object in the DIA object table.

Forced photometry on difference images is expected to behave best, especially in crowded regions, since image subtraction should remove neighbors even more effectively than the deblender run on the coadds. There is no deblending whatsoever in forced photometry on visit images. See also Forced source for a description of the four forced photometry variants.

Processing#

The DIA forced source table is the result of Difference image analysis (DIA).

Tutorials#

See the 200-level catalog Tutorials for a notebook on the DIA forced source table.