Connection to image mask planes#

Catalog pixelFlags_* columns are derived directly from the image mask planes. Each relevant mask-plane bit set in the pixels of a source’s footprint propagates to the corresponding pixel flag in the catalog.

New for DP2: Several mask plane names have been updated to be more descriptive; the legacy (old) and new mask names are listed below. Note that the catalog pixelFlags_* columns use the legacy names.

Legacy (old) to new mask names:

SAT → SATURATED
CR → COSMIC_RAY
INTRP → INTERPOLATED
EDGE → DETECTION_EDGE

Coadd image mask planes#

The mapping below connects the mask planes for the deep coadd images and the Object catalog, which contains detections and measurements in the deep coadd images.

Key points: Flags without a Center suffix are set if any pixel in the source footprint carries the mask bit; Center flags are set only if a pixel in the central 3×3 box carries it. For quality filtering, center flags are usually the more important because they affect the core photometry and shape.

New for DP2: For cell-based coadds, pixels at the edge of the input detector images do not contribute to the coadded image. The relevant coadd mask plane (DETECTION_EDGE) and corresponding Object catalog flags (e.g., pixelFlags_edge) are not included in the table below.

Mask plane (new and legacy)	Object catalog flag	Notes
`NO_DATA` `NO_DATA`	`pixelFlags_nodata`	No usable data at this location; check for coverage.
`INTERPOLATED` `INTRP`	`pixelFlags_interpolated`	Pixel value interpolated from neighbors, anywhere in the footprint.
`INTERPOLATED` `INTRP`	`pixelFlags_interpolatedCenter`	Interpolated pixel in the central 3×3 box.
`COSMIC_RAY` `CR`	`pixelFlags_cr`	Cosmic ray on ≥1 input (interpolated over), anywhere in the footprint.
`COSMIC_RAY` `CR`	`pixelFlags_crCenter`	Cosmic ray in the central 3×3 box.
`SATURATED` `SAT`	`pixelFlags_saturated`	>10% of potential inputs saturated here; implies `REJECTED`.
`SATURATED` `SAT`	`pixelFlags_saturatedCenter`	Saturation in the central 3×3 box.
`CLIPPED` `CLIPPED`	`pixelFlags_clipped`	Probable artifact rejected in coaddition; implies `REJECTED`.
`CLIPPED` `CLIPPED`	`pixelFlags_clippedCenter`	Clipping occurred in the central 3×3 box.
`REJECTED` `REJECTED`	(no dedicated catalog flag)	An input visit was left out at this pixel due to masking; implied by `CLIPPED` and `INEXACT_PSF`.
`INEXACT_PSF` `INEXACT_PSF`	`pixelFlags_inexact_psf`	PSF may be inexact; covers a large area, not recommended as a general cut.
`INEXACT_PSF` `INEXACT_PSF`	`pixelFlags_inexact_psfCenter`	Inexact PSF in the central 3×3 box.
`DETECTED` `DETECTED`	(no quality flag; see `detect_*` columns)	Pixel is part of a detected source footprint.

Visit and difference image mask planes#

The mask planes for the visit and difference images are connected with the Source, ForcedSource, DiaSource, and ForcedSourceOnDiaObject catalogs.

These catalogs contain pixelFlags_* columns derived from the visit-image and difference-image mask planes — for example pixelFlags_bad, pixelFlags_suspect, pixelFlags_edge.

For DiaSource, there are additional derived columns such as pixelFlags_streak.