Catalog flag columns

Catalog tables contain extensive boolean flag columns that indicate quality issues, processing failures, or special conditions identified during Science Pipelines processing. These flags are provided for users to apply as quality filters based on their science requirements. Catalog data is delivered largely “as measured” with minimal a priori filtering, since the appropriate flag criteria depend on the specific science case.

• Flag definitions and categories
• Flag usage guidance
• Connection to image mask planes

What is a flag column?

A flag column is a boolean (True/False) column in a catalog table that indicates whether a specific condition, issue, or failure occurred during measurement or processing.

The key characteristics of flag columns are the following.

• Data type: Boolean (bool or boolean in the schema).

• Naming convention: Most flag columns have flag in the column name (e.g., psfFlux_flag, pixelFlags_saturated). Some flags, such as those related to calibration (calib_*), do not include “flag” in their name. The naming pattern is typically {band}_{measurement}_flag for the Object table and {measurement}_flag for Source-level tables.

• Interpretation: 1 (True) indicates the condition occurred or the measurement failed; 0 (False) indicates success or absence of the issue.

• Usage: Users typically filter out rows where critical flags are set to 1 to obtain clean, science-quality samples.