Inside catalogs: a comparison of source extraction software

TL;DR

This paper compares the performance of SExtractor with PSFEx against DAOPHOT with ALLSTAR for source extraction in simulated images, highlighting their respective strengths in star/galaxy separation, photometry, and catalog completeness.

Contribution

It demonstrates that the new SExtractor+PSFEx combination is competitive with DAOPHOT, especially for galaxy characterization and faint source detection.

Findings

SExtractor+PSFEx produces deeper catalogs than DAOPHOT.

Neural networks and SPREAD_MODEL improve star/galaxy separation.

Performance declines in crowded fields for both software.

Abstract

The scope of this paper is to compare the catalog extraction performances obtained using the new combination of SExtractor with PSFEx, against the more traditional and diffuse application of DAOPHOT with ALLSTAR; therefore, the paper may provide a guide for the selection of the most suitable catalog extraction software. Both software packages were tested on two kinds of simulated images having, respectively, a uniform spatial distribution of sources and an overdensity in the center. In both cases, SExtractor is able to generate a deeper catalog than DAOPHOT. Moreover, the use of neural networks for object classification plus the novel SPREAD\_MODEL parameter push down to the limiting magnitude the possibility of star/galaxy separation. DAOPHOT and ALLSTAR provide an optimal solution for point-source photometry in stellar fields and very accurate and reliable PSF photometry, with robust star-galaxy separation. However, they are not useful for galaxy characterization, and do not generate catalogs that are very complete for faint sources. On the other hand, SExtractor, along with the new capability to derive PSF photometry, turns to be competitive and returns accurate photometry also for galaxies. We can assess that the new version of SExtractor, used in conjunction with PSFEx, represents a very powerful software package for source extraction with performances comparable to those of DAOPHOT. Finally, by comparing the results obtained in the case of a uniform and of an overdense spatial distribution of stars, we notice, for both software packages, a decline for the latter case in the quality of the results produced in terms of magnitudes and centroids.