Inside Catalogs: A Comparison of Source Extraction Software

Abstract

The scope of this article 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 a uniform spatial distribution of sources and an overdensity in the center, respectively. 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 out to be competitive and returns accurate photometry for galaxies also. We can report 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 cases 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.

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