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Published July 2012 | Published
Journal Article Open

Aperture Photometry Tool Versus SExtractor for Noncrowded Fields

Abstract

Outputs from new software program Aperture Photometry Tool (APT) are compared with similar outputs from SExtractor for sources extracted from R-band optical images acquired by the Palomar Transient Factory (PTF), infrared mosaics constructed from Spitzer Space Telescope images, and a processed visible/near-infrared image from the Hubble Legacy Archive (HLA). Two large samples from the PTF images are studied, each containing around 3 × 10^3 sources from noncrowded fields. The median values of source-intensity relative percentage differences between the two software programs, computed separately for two PTF samples, are +0.13% and +0.17%, with corresponding statistical dispersions of 1.43% and 1.84%, respectively. For the Spitzer mosaics, a similar large sample of extracted sources for each of channels 1–4 of Spitzer's Infrared Array Camera (IRAC) are analyzed with two different sky annulus sizes, and we find that the median and modal values of source-intensity relative percentage differences between the two software programs are between -0.5% and +2.0%, and the corresponding statistical dispersions range from 1.4 to 6.7%, depending on the Spitzer IRAC channel and sky annulus. The results for the HLA image are mixed, as might be expected for a moderately crowded field. The comparisons for the three different kinds of images show that there is generally excellent agreement between APT and SExtractor. Differences in source-intensity uncertainty estimates for the PTF images amount to less than 3% for the PTF sources, and these are potentially caused by SExtractor's omission of the sky background uncertainty term in the formula for source-intensity uncertainty, as well as differing methods of sky background estimation.

Additional Information

© 2012 Astronomical Society of the Pacific. Received 2010 March 29; accepted 2012 April 27; published 2012 June 18. This work is based in part on images acquired by the Palomar Transient Factory; in part on archival data obtained with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (NASA); and in part on observations made with the NASA/ESA Hubble Space Telescope and obtained from the Hubble Legacy Archive, which is a collaboration between the Space Telescope Science Institute (STScI/NASA), the Space Telescope European Coordinating Facility (ST-ECF/ESA), and the Canadian Astronomy Data Centre (CADC/NRC/CSA). This research made use of Montage, funded by NASA's Earth Science Technology Office, Computation Technologies Project, under cooperative agreement NCC5-626 between NASA and the California Institute of Technology. Montage is maintained by the NASA/IPAC Infrared Science Archive.

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Created:
August 19, 2023
Modified:
October 19, 2023