Astrometric calibration and performance of the Dark Energy Camera

TL;DR

This paper evaluates the astrometric precision of the Dark Energy Camera over four years, modeling various distortions and atmospheric effects, achieving milliarcsecond accuracy in stellar position measurements.

Contribution

It presents a comprehensive empirical model of astrometric errors in DECam, including optical, electronic, and atmospheric factors, improving calibration accuracy.

Findings

Atmospheric turbulence causes 10-30 mas errors with 5-10 arcmin coherence.

Calibration achieves 3-6 mas accuracy per exposure using Gaia reference catalog.

Residual errors are dominated by atmospheric and electronic effects.

Abstract

We characterize the ability of the Dark Energy Camera (DECam) to perform relative astrometry across its 500~Mpix, 3 deg^2 science field of view, and across 4 years of operation. This is done using internal comparisons of ~4x10^7 measurements of high-S/N stellar images obtained in repeat visits to fields of moderate stellar density, with the telescope dithered to move the sources around the array. An empirical astrometric model includes terms for: optical distortions; stray electric fields in the CCD detectors; chromatic terms in the instrumental and atmospheric optics; shifts in CCD relative positions of up to ~10 um when the DECam temperature cycles; and low-order distortions to each exposure from changes in atmospheric refraction and telescope alignment. Errors in this astrometric model are dominated by stochastic variations with typical amplitudes of 10-30 mas (in a 30 s exposure) and 5-10 arcmin coherence length, plausibly attributed to Kolmogorov-spectrum atmospheric turbulence. The size of these atmospheric distortions is not closely related to the seeing. Given an astrometric reference catalog at density ~0.7 arcmin^{-2}, e.g. from Gaia, the typical atmospheric distortions can be interpolated to 7 mas RMS accuracy (for 30 s exposures) with 1 arcmin coherence length for residual errors. Remaining detectable error contributors are 2-4 mas RMS from unmodelled stray electric fields in the devices, and another 2-4 mas RMS from focal plane shifts between camera thermal cycles. Thus the astrometric solution for a single DECam exposure is accurate to 3-6 mas (0.02 pixels, or 300 nm) on the focal plane, plus the stochastic atmospheric distortion.

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Full text

Astrometric calibration and performance of the Dark Energy Camera

G. M. Bernstein11affiliation: Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104, USA , R. Armstrong22affiliation: Department of Astrophysical Sciences, Princeton University, Peyton Hall, Princeton, NJ 08544, USA , A. A. Plazas33affiliation: Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109, USA , A. R. Walker44affiliation: Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, Casilla 603, La Serena, Chile , T. M. C. Abbott44affiliation: Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, Casilla 603, La Serena, Chile , S. Allam55affiliation: Fermi National Accelerator Laboratory, P. O. Box 500, Batavia, IL 60510, USA , K. Bechtol66affiliation: LSST, 933 North Cherry Avenue, Tucson, AZ 85721, USA , A. Benoit-Lévy77affiliation: CNRS, UMR 7095, Institut d’Astrophysique de Paris, F-75014, Paris, France 88affiliation: Department of Physics & Astronomy, University College London, Gower Street, London, WC1E 6BT, UK 99affiliation: Sorbonne Universités, UPMC Univ Paris 06, UMR 7095, Institut d’Astrophysique de Paris, F-75014, Paris, France , D. Brooks88affiliation: Department of Physics & Astronomy, University College London, Gower Street, London, WC1E 6BT, UK , D. L. Burke1010affiliation: Kavli Institute for Particle Astrophysics & Cosmology, P. O. Box 2450, Stanford University, Stanford, CA 94305, USA 1111affiliation: SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA , A. Carnero Rosell1212affiliation: Laboratório Interinstitucional de e-Astronomia - LIneA, Rua Gal. José Cristino 77, Rio de Janeiro, RJ - 20921-400, Brazil 1313affiliation: Observatório Nacional, Rua Gal. José Cristino 77, Rio de Janeiro, RJ - 20921-400, Brazil , M. Carrasco Kind1414affiliation: Department of Astronomy, University of Illinois, 1002 W. Green Street, Urbana, IL 61801, USA 1515affiliation: National Center for Supercomputing Applications, 1205 West Clark St., Urbana, IL 61801, USA , J. Carretero1616affiliation: Institut de Física d’Altes Energies (IFAE), The Barcelona Institute of Science and Technology, Campus UAB, 08193 Bellaterra (Barcelona) Spain , C. E. Cunha1010affiliation: Kavli Institute for Particle Astrophysics & Cosmology, P. O. Box 2450, Stanford University, Stanford, CA 94305, USA , L. N. da Costa1212affiliation: Laboratório Interinstitucional de e-Astronomia - LIneA, Rua Gal. José Cristino 77, Rio de Janeiro, RJ - 20921-400, Brazil 1313affiliation: Observatório Nacional, Rua Gal. José Cristino 77, Rio de Janeiro, RJ - 20921-400, Brazil , D. L. DePoy1717affiliation: George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, and Department of Physics and Astronomy, Texas A&M University, College Station, TX 77843, USA , S. Desai1818affiliation: Department of Physics, IIT Hyderabad, Kandi, Telangana 502285, India , H. T. Diehl55affiliation: Fermi National Accelerator Laboratory, P. O. Box 500, Batavia, IL 60510, USA , T. F. Eifler33affiliation: Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109, USA , E. Fernandez1616affiliation: Institut de Física d’Altes Energies (IFAE), The Barcelona Institute of Science and Technology, Campus UAB, 08193 Bellaterra (Barcelona) Spain , P. Fosalba1919affiliation: Institut de Ciències de l’Espai, IEEC-CSIC, Campus UAB, Carrer de Can Magrans, s/n, 08193 Bellaterra, Barcelona, Spain , J. Frieman55affiliation: Fermi National Accelerator Laboratory, P. O. Box 500, Batavia, IL 60510, USA 2020affiliation: Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637, USA , J. García-Bellido2121affiliation: Instituto de Fisica Teorica UAM/CSIC, Universidad Autonoma de Madrid, 28049 Madrid, Spain , D. W. Gerdes2222affiliation: Department of Astronomy, University of Michigan, Ann Arbor, MI 48109, USA 2323affiliation: Department of Physics, University of Michigan, Ann Arbor, MI 48109, USA , D. Gruen1010affiliation: Kavli Institute for Particle Astrophysics & Cosmology, P. O. Box 2450, Stanford University, Stanford, CA 94305, USA 1111affiliation: SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA , R. A. Gruendl1414affiliation: Department of Astronomy, University of Illinois, 1002 W. Green Street, Urbana, IL 61801, USA 1515affiliation: National Center for Supercomputing Applications, 1205 West Clark St., Urbana, IL 61801, USA , J. Gschwend1212affiliation: Laboratório Interinstitucional de e-Astronomia - LIneA, Rua Gal. José Cristino 77, Rio de Janeiro, RJ - 20921-400, Brazil 1313affiliation: Observatório Nacional, Rua Gal. José Cristino 77, Rio de Janeiro, RJ - 20921-400, Brazil , G. Gutierrez55affiliation: Fermi National Accelerator Laboratory, P. O. Box 500, Batavia, IL 60510, USA , K. Honscheid2424affiliation: Center for Cosmology and Astro-Particle Physics, The Ohio State University, Columbus, OH 43210, USA 2525affiliation: Department of Physics, The Ohio State University, Columbus, OH 43210, USA , D. J. James2626affiliation: Astronomy Department, University of Washington, Box 351580, Seattle, WA 98195, USA 44affiliation: Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, Casilla 603, La Serena, Chile , S. Kent55affiliation: Fermi National Accelerator Laboratory, P. O. Box 500, Batavia, IL 60510, USA 2020affiliation: Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637, USA , E. Krause1010affiliation: Kavli Institute for Particle Astrophysics & Cosmology, P. O. Box 2450, Stanford University, Stanford, CA 94305, USA , K. Kuehn2727affiliation: Australian Astronomical Observatory, North Ryde, NSW 2113, Australia , N. Kuropatkin55affiliation: Fermi National Accelerator Laboratory, P. O. Box 500, Batavia, IL 60510, USA , T. S. Li55affiliation: Fermi National Accelerator Laboratory, P. O. Box 500, Batavia, IL 60510, USA 1717affiliation: George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, and Department of Physics and Astronomy, Texas A&M University, College Station, TX 77843, USA , M. A. G. Maia1212affiliation: Laboratório Interinstitucional de e-Astronomia - LIneA, Rua Gal. José Cristino 77, Rio de Janeiro, RJ - 20921-400, Brazil 1313affiliation: Observatório Nacional, Rua Gal. José Cristino 77, Rio de Janeiro, RJ - 20921-400, Brazil , M. March11affiliation: Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104, USA , J. L. Marshall1717affiliation: George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, and Department of Physics and Astronomy, Texas A&M University, College Station, TX 77843, USA , F. Menanteau1414affiliation: Department of Astronomy, University of Illinois, 1002 W. Green Street, Urbana, IL 61801, USA 1515affiliation: National Center for Supercomputing Applications, 1205 West Clark St., Urbana, IL 61801, USA , R. Miquel2828affiliation: Institució Catalana de Recerca i Estudis Avançats, E-08010 Barcelona, Spain 1616affiliation: Institut de Física d’Altes Energies (IFAE), The Barcelona Institute of Science and Technology, Campus UAB, 08193 Bellaterra (Barcelona) Spain , R. L. C. Ogando1212affiliation: Laboratório Interinstitucional de e-Astronomia - LIneA, Rua Gal. José Cristino 77, Rio de Janeiro, RJ - 20921-400, Brazil 1313affiliation: Observatório Nacional, Rua Gal. José Cristino 77, Rio de Janeiro, RJ - 20921-400, Brazil , K. Reil1111affiliation: SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA , A. Roodman1010affiliation: Kavli Institute for Particle Astrophysics & Cosmology, P. O. Box 2450, Stanford University, Stanford, CA 94305, USA 1111affiliation: SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA , E. S. Rykoff1010affiliation: Kavli Institute for Particle Astrophysics & Cosmology, P. O. Box 2450, Stanford University, Stanford, CA 94305, USA 1111affiliation: SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA , E. Sanchez2929affiliation: Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), Madrid, Spain , V. Scarpine55affiliation: Fermi National Accelerator Laboratory, P. O. Box 500, Batavia, IL 60510, USA , R. Schindler1111affiliation: SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA , M. Schubnell2323affiliation: Department of Physics, University of Michigan, Ann Arbor, MI 48109, USA , I. Sevilla-Noarbe2929affiliation: Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), Madrid, Spain , M. Smith3030affiliation: School of Physics and Astronomy, University of Southampton, Southampton, SO17 1BJ, UK , R. C. Smith44affiliation: Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, Casilla 603, La Serena, Chile , M. Soares-Santos55affiliation: Fermi National Accelerator Laboratory, P. O. Box 500, Batavia, IL 60510, USA , F. Sobreira1212affiliation: Laboratório Interinstitucional de e-Astronomia - LIneA, Rua Gal. José Cristino 77, Rio de Janeiro, RJ - 20921-400, Brazil 3131affiliation: Universidade Federal do ABC, Centro de Ciências Naturais e Humanas, Av. dos Estados, 5001, Santo André, SP, Brazil, 09210-580 , E. Suchyta3232affiliation: Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 , M. E. C. Swanson1515affiliation: National Center for Supercomputing Applications, 1205 West Clark St., Urbana, IL 61801, USA , G. Tarle2323affiliation: Department of Physics, University of Michigan, Ann Arbor, MI 48109, USA

(DES Collaboration)

astrometry—atmospheric effects—methods: data analysis—instrumentation: detectors

††slugcomment: Version 1.1, Submitted to PASP