Pixel-based correction for Charge Transfer Inefficiency in the Hubble Space Telescope Advanced Camera for Surveys |
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| Authors: | Richard Massey Chris Stoughton Alexie Leauthaud Jason Rhodes Anton Koekemoer Richard Ellis Edgar Shaghoulian |
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| Affiliation: | Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ;Fermi National Accelerator Laboratory, PO Box 500, Batavia, IL 60510, USA;Physics Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA;Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA;California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA;Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA;Stanford University, Physics building, 382 Via Pueblo Mall, Stanford, CA 94305, USA |
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| Abstract: | Charge Transfer Inefficiency (CTI) due to radiation damage above the Earth's atmosphere creates spurious trailing in Hubble Space Telescope ( HST ) images. Radiation damage also creates unrelated warm pixels – but these happen to be perfect for measuring CTI. We model CTI in the Advanced Camera for Surveys (ACS)/Wide Field Channel and construct a physically motivated correction scheme. This operates on raw data, rather than secondary science products, by returning individual electrons to pixels from which they were unintentionally dragged during readout. We apply our correction to images from the HST Cosmic Evolution Survey (COSMOS), successfully reducing the CTI trails by a factor of ∼30 everywhere in the CCD and at all flux levels. We quantify changes in galaxy photometry, astrometry and shape. The remarkable 97 per cent level of correction is more than sufficient to enable a (forthcoming) reanalysis of downstream science products and the collection of larger surveys. |
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| Keywords: | instrumentation: detectors methods: data analysis space vehicles: instruments |
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