PSFEx

PSFEx
Name	PSFEx
Developer	Astr Omatic / Emmanuel Bertin
Released	2013
Programming language	C++
Operating system	Unix-like
License	GNU GPL

PSFEx is a software tool for modeling the point spread function used in astronomical image analysis. It generates spatially varying models of point sources to support tasks such as source extraction, photometry, and astrometry. PSFEx is commonly used within pipelines that include tools from the astronomical data reduction and survey communities.

Overview

PSFEx was created to complement image analysis packages and survey projects including SExtractor, CFHTLS, Pan-STARRS, SDSS, DES, LSST, VISTA, Euclid and Gaia processing chains. The project draws on methods used by teams at institutions such as Centro de Astrobiología, European Southern Observatory, National Optical Astronomy Observatory, Institut d'Astrophysique de Paris and Institut de Recherche en Astrophysique et Planétologie. It is widely adopted by collaborations working with instruments at observatories like Very Large Telescope, Subaru Telescope, Canada–France–Hawaii Telescope and survey facilities operated by Max Planck Society and National Aeronautics and Space Administration. PSFEx integrates with cataloging efforts tied to archives such as VizieR, STScI, IPAC and CADC.

Algorithm and Model

PSFEx models the point spread function using basis expansions and spatial interpolation methods that are comparable to approaches used in software developed by teams at JPL, Harvard–Smithsonian Center for Astrophysics, Lawrence Berkeley National Laboratory, CERN groups and university consortia. Its core algorithms combine principal components, pixel basis functions and polynomial surfaces similar to techniques applied in studies by Stanford University, Caltech, MIT, University of Cambridge and University of Oxford groups. Regularization strategies in PSFEx resemble methods discussed at conferences such as American Astronomical Society meetings and in proceedings from SPIE. The modeling framework supports multi-component representations that echo approaches used for point-source reconstruction in programs affiliated with European Space Agency, Space Telescope Science Institute and national research labs.

Input Data and Configuration

Input catalogs and images for PSFEx originate from image detectors and pipelines at facilities like Subaru Telescope's Suprime-Cam, VISTA's VIRCAM, CFHT's MegaCam, DECam on Blanco Telescope and sensors used in Keck Observatory instruments. Typical inputs include catalogs produced by SExtractor, photometric measurements linked to calibrations from Pan-STARRS and astrometric references tied to Gaia catalogs. Configuration files reference parameters and tables used in survey pipelines developed by groups at IPAC, NOAO, ESO, LSST Corporation and academic teams at Princeton University, University of Washington and Carnegie Institution for Science.

Applications and Use Cases

PSFEx is applied in photometric pipelines and weak-lensing analyses within projects like DES, KiDS, HSC Survey, Euclid Consortium and preparations for LSST. It supports tasks such as point-source photometry used by groups at IPAC, deblending studies relevant to Hubble Space Telescope datasets, and astrometric refinement for cross-matching with Gaia and 2MASS. Survey science cases include galaxy morphology studies tied to teams at Max Planck Institute for Astronomy, transient detection pipelines used by collaborations with Zwicky Transient Facility and exoplanet transit photometry supported by observers at Harvard University and University of California, Berkeley.

Performance and Validation

Validation of PSFEx models is typically performed in the context of survey validation efforts like those undertaken by DES Collaboration, LSST Science Collaborations, Pan-STARRS1 Science Consortium and programs at STScI. Performance evaluations compare PSFEx outputs against methods developed at institutions such as Institute for Astronomy, University of Edinburgh, Kavli Institute for Particle Astrophysics and Cosmology and Fermi National Accelerator Laboratory. Metrics include residual analysis used in weak-lensing systematics budgets reported at American Astronomical Society meetings and image quality assessments referenced in publications from SPIE proceedings and journals associated with IOP Publishing and Oxford University Press.

Development and Integration

Development has involved contributors from individual researchers and teams at organizations like Institut d'Astrophysique de Paris, University of Oxford, CNRS laboratories, CEA groups and independent developers aligned with projects such as Astromatic. Integration work ensures compatibility with data reduction environments at STScI, NOAO, IPAC and survey data centers managed by NERSC and CANFAR. PSFEx is packaged and distributed for use in Unix-like environments and is included in software stacks used by observatories and collaborations such as ESO, ALMA partner institutions, and national facilities funded by agencies like NSF and NASA.

Category:Astronomy software