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Title: Characterization and correction of charge-induced pixel shifts in DECam

Interaction of charges in CCDs with the already accumulated charge distribution causes both a flux dependence of the point-spread function (an increase of observed size with flux, also known as the brighter/fatter effect) and pixel-to-pixel correlations of the Poissonian noise in flat fields. We describe these effects in the Dark Energy Camera (DECam) with charge dependent shifts of effective pixel borders, i.e. the Antilogus et al. (2014) model, which we fit to measurements of flat-field Poissonian noise correlations. The latter fall off approximately as a power-law r-2.5 with pixel separation r, are isotropic except for an asymmetry in the direct neighbors along rows and columns, are stable in time, and are weakly dependent on wavelength. They show variations from chip to chip at the 20% level that correlate with the silicon resistivity. The charge shifts predicted by the model cause biased shape measurements, primarily due to their effect on bright stars, at levels exceeding weak lensing science requirements. We measure the flux dependence of star images and show that the effect can be mitigated by applying the reverse charge shifts at the pixel level during image processing. Differences in stellar size, however, remain significant due to residuals at larger distancemore » from the centroid.« less
Authors:
 [1] ;  [2] ;  [2] ;  [3] ;  [4] ;  [5] ;  [1]
  1. Univ. Observatory Munich (Germany); Max Planck Inst. fur Extraterrestrische Physik, Garching (Germany)
  2. Univ. of Pennsylvania, Philadelphia, PA (United States)
  3. Univ. College London, London (United Kingdom)
  4. Univ. of Pennsylvania, Philadelphia, PA (United States); Argonne National Lab. (ANL), Argonne, IL (United States)
  5. Brookhaven National Lab. (BNL), Upton, NY (United States); California Inst. of Technology (CalTech), La Canada Flintridge, CA (United States). Jet Propulsion Lab.
Publication Date:
OSTI Identifier:
1226044
Report Number(s):
BNL--108406-2015-JA
Journal ID: ISSN 1748-0221; KA2301020
Grant/Contract Number:
SC00112704
Type:
Accepted Manuscript
Journal Name:
Journal of Instrumentation
Additional Journal Information:
Journal Volume: 10; Journal ID: ISSN 1748-0221
Publisher:
Institute of Physics (IOP)
Research Org:
Brookhaven National Lab. (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS