Abstract
We present a new method to measure photometry zero-points using high redshift red-sequence galaxies. This method allows us to measure the HST NICMOS F110W zero-point close to the sky level and, thus, avoid calibration errors due to the poorly constrained HgCdTe non-linearity at these faint flux levels. This is the level at which almost all of the highest redshift supernovae observations are obtained with NICMOS camera. We combine space optical observations (HST ACS i775 and z850) and ground based near infrared observation (VLT HAWKI/ISAAC J and K) to constrain galaxy SED and thus derived synthetic photometry for NICMOS F110W. Finally, with the derived synthetic photometry, we compute the zero-point from the observed fluxes in F110W. Using only 20 red-sequence galaxies, we can achieve a 2% calibration at requisite faint flux level. This work has been supported by the Office of Science, U.S. Department of Energy, through contract DE-AC02-05CH11231 and in part by NASA through grants associated with HST-GO-10496 and HST-GO-11799.
Original language | English |
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Pages | 462.01 |
Publication status | Published - 1 Jan 2010 |