Processing

The complete analysis of an image is fully automated (Fig. 4). There are three main steps in the processing: detection, collection and measurement:

• During the detection step, image pixels from the detection image are background-subtracted, filtered and segmented on-the-fly. The extracted source candidates are then deblended.

• During the collection step, a source model is fit to the detection image. Overlapping sources are identified, grouped and pruned (“cleaned”).

• During the measurement step, sources are analysed individually or as part of their group. Measurements are written to the output catalog.

Fig. 4 Layout of the main SourceXtractor++ procedures. Dashed arrows represent optional inputs.

The following sections describe each of these operations in more detail.

• Modeling the background
  • Background estimation
  • Background map
  • Configuration and tuning
  • Computing cost
• Weighting
  • Effect of weighting
  • Weight-map formats
    • Detection weight-map
    • Measurement weight-map
• Flagging
  • External flags