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WFC3 Photometric Zeropoints

For WFC3, zeropoints represent the flux or magnitude corresponding to a (flat-field corrected) count rate of 1 electron per second, and are used to convert instrumental to astrophysical units.

The tables below are the derived quantities from observations of GD153, G191B2B, GD71, and P330E acquired between 2009 and 2012. The independent calibrations from the four stars agree to within 1% in most filters, and the photometric zeropoint is set to the average of the measurements. The data sets were processed with AstroDrizzle.

The methodology used to determine the zeropoints will be described in a forthcoming ISR.

Zeropoint tables after March 06, 2012:

The methodology used to determine the zeropoints will be described in a forthcoming ISR.

Zeropoint tables after March 06, 2012:

For an infinite aperture:

IR

IR

For a 0.4 arcsec radius aperture:

IR

IR

Zeropoint tables prior to March 06, 2012:

IR
IR

Aperture Corrections and Encircled Energy Curves

Aperture Corrections and EE curves for WFC3/IR

Photometric Systems:

Photometric Keywords in the SCI extention of WFC3 images:

(keywords affected by the sensitivity curve update are highlighted) The header keywords PHOTFLAM and PHOTPLAM relate to the STMAG and ABMAG zeropoints through the formulae:

Users performing photometry on non-drizzled _flt images may wish to read the description of the pixel area map.

Created 09/09/2009 MJD
Modified 03/06/2012 by CMP