This page details the meaning of the bitmasks provided with Data Release 8 of the Legacy Surveys. The bits are enumerated as a power (i.e. 7 written in a column of bits means two-to-the-power-of-7).

BRIGHTBLOB

See also the legacypipe bitmask definitions. Note that the difference between bits 0, 1, 2, 3 for BRIGHTBLOB as compared to bits 1, 11, 12 and 13 for MASKBITS is that BRIGHTBLOB is set based on an initial position (the source detection integer pixel peak), while MASKBITS is set after fitting has finished (i.e., on the final brick pixel position). This can lead to slight differences (~0.15%) in the areas covered by the MASKBITS and BRIGHTBLOB masks.

Bit Name Description
0 BRIGHT source lies in the pixels that define a bright star (Tycho)
1 MEDIUM source lies in the pixels that define medium bright star (GAIA)
2 CLUSTER source lies in the pixels that define a globular cluster
3 GALAXY source lies in the pixels that define an SGA large galaxy

Bit Name Description
0 NPRIMARY touches a pixel that is outside the BRICK_PRIMARY region of a brick
1 BRIGHT touches a pixel within the locus of a radius-magnitude relation for Tycho-2 stars or one for Gaia DR2 stars to G < 13
2 SATUR_G touches a pixel that was saturated in at least one $g$-band image
3 SATUR_R touches a pixel that was saturated in at least one $r$-band image
4 SATUR_Z touches a pixel that was saturated in at least one $z$-band image
5 ALLMASK_G touches a pixel that has any of the ALLMASK_G bits set
6 ALLMASK_R touches a pixel that has any of the ALLMASK_R bits set
7 ALLMASK_Z touches a pixel that has any of the ALLMASK_Z bits set
10 BAILOUT touches a pixel in a blob where we "bailed out" of source fitting
11 MEDIUM touches a pixel within the locus of a radius-magnitude relation for Gaia DR2 stars to G < 16
12 GALAXY touches a pixel in an SGA large galaxy
13 CLUSTER touches a pixel in a globular cluster

ANYMASK_X denotes a source that touches a bad pixel in any of a set of overlapping $X$-band images whereas ALLMASK_X denotes a source that touches a bad pixel in all of a set of overlapping $X$-band images. See, also, the legacypipe bitmask definitions. The ANYMASK and ALLMASK bit masks are defined as follows, mostly from the CP (NOIRLab Community Pipeline) Data Quality bits, which we map to the values in the table.

Bit Name Description
1 SATUR saturated
2 INTERP interpolated
4 CR single exposure cosmic ray
6 BLEED bleed trail
7 TRANS multi-exposure transient
8 EDGE edge pixel
9 EDGE2 edge pixel
11 OUTLIER marked as touching an outlier pixel by legacypipe itself