WFPC2 CTE for Extended Sources: I. Photometric Correction
ثبت نشده
چکیده
We measure the effects of charge transfer efficiency (CTE) losses on resolved sources in Wide Field and Planetary Camera 2 (WFPC2) images from 1995 to 2008. We compare medium and long exposures of the Hubble Deep Field – North taken with the F606W filter at several epochs against a “truth” mosaic of the field taken with the Advanced Camera for Surveys early in that instrument’s operation. We adopt the Dolphin (2009) functional form for the CTE photometric correction and determine the optimal coefficients for extended sources on the Wide Field (WF) detectors as a function of observation date, pre-corrected source flux, background flux, and source position on the detector.
منابع مشابه
The Dependence of WFPC2 Charge Transfer Efficiency on Background Illumination
We have examined the charge transfer efficiency (CTE) of WFPC2's CCDs near the end of mission as a function of background illumination. Internal lamps were used to flash the CCDs before or after external exposures of ! Cen to produce average background signals of 0–160 e. These signals span the natural sky backgrounds observed in ~99% of archived WFPC2 science images. Most of the stellar flux l...
متن کاملWFPC2 CTE Characterization
The limiting factor of the accuracy of WFPC2 photometry is the CTE loss, which has increased to the level of 50% or more for faint stars at the top of the chips. I describe recent work on characterizing this effect, and provide improved equations for CTE correction. I also examine issues affecting background measurement, which if not done correctly can introduce artificial nonlinearities into p...
متن کاملHot Pixels as a Probe of WFPC2 CTE Effects
Hot pixels provide a potentially useful probe of CTE effects, as they can be used to measure effects at the smallest scales -at single pixel level. Herein we outline a method of using the tails on hot pixels to quantify CTE effects, and apply it to CTE tails in WFPC2 dark frames. As we show, many of the behaviors associated with photometric CTE are also found for hot pixel tails including the d...
متن کاملThe Charge Transfer Efficiency and Calibration of WFPC 2 Andrew
A new determination of WFPC2 photometric corrections is presented, using HSTphot reduction of the WFPC2 Omega Centauri and NGC 2419 observations from January 1994 through March 2000 and a comparison with ground-based photometry. No evidence is seen for any position-independent photometric offsets (the " long-short anomaly "); all systematic errors appear to be corrected with the CTE and zero po...
متن کاملThe Charge Transfer Efficiency and Calibration of WFPC 2
A new determination of WFPC2 photometric corrections is presented, using HSTphot reduction of the WFPC2 Omega Centauri and NGC 2419 observations from January 1994 through March 2000 and a comparison with ground-based photometry. No evidence is seen for any position-independent photometric offsets (the " long-short anomaly "); all systematic errors appear to be corrected with the CTE and zero po...
متن کامل