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Calibration of HST wide field camera for quantitative analysis of faint galaxy imagesWe present the methods adopted to optimize the calibration of images obtained with the Hubble Space Telescope (HST) Wide Field Camera (WFC) (1991-1993). Our main goal is to improve quantitative measurement of faint images, with special emphasis on the faint (I approximately 20-24 mag) stars and galaxies observed as a part of the Medium-Deep Survey. Several modifications to the standard calibration procedures have been introduced, including improved bias and dark images, and a new supersky flatfield obtained by combining a large number of relatively object-free Medium-Deep Survey exposures of random fields. The supersky flat has a pixel-to-pixel rms error of about 2.0% in F555W and of 2.4% in F785LP; large-scale variations are smaller than 1% rms. Overall, our modifications improve the quality of faint images with respect to the standard calibration by about a factor of five in photometric accuracy and about 0.3 mag in sensitivity, corresponding to about a factor of two in observing time. The relevant calibration images have been made available to the scientific community.
Document ID
19950043845
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Ratnatunga, Kavan U.
(Johns Hopkins University Baltimore, MD, United States)
Griffiths, Richard E.
(Johns Hopkins University Baltimore, MD, United States)
Casertano, Stefano
(Johns Hopkins University Baltimore, MD, United States)
Neuschaefer, Lyman W.
(Johns Hopkins University Baltimore, MD, United States)
Wyckoff, Eric W.
(Johns Hopkins University Baltimore, MD, United States)
Date Acquired
August 16, 2013
Publication Date
December 1, 1994
Publication Information
Publication: Astronomical Journal
Volume: 108
Issue: 6
ISSN: 0004-6256
Subject Category
Astronomy
Accession Number
95A75444
Funding Number(s)
CONTRACT_GRANT: NAS5-26555
Distribution Limits
Public
Copyright
Other

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