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K.A.G. Olsen, R.D. Blum (NOAO), F. Rigaut (Gemini Observatory)
We present a study of the effect of crowding on stellar photometry. We develop an analytical model through which we are able to predict the error in magnitude and color for a given star for any telescope resolution, luminosity function, surface brightness, and distance of the stellar background. We test our predictions with Monte Carlo simulations of the LMC globular cluster NGC 1835, for resolutions corresponding to a seeing-limited 1.5-m telescope, the HST, and an AO-corrected 30-m (near diffraction limited) telescope. Our analytically predicted magnitude errors agree with the simulation results to within ~20%. The analytical model also predicts that errors in color are strongly affected by the correlation of crowding--induced photometric errors between bands as is seen in the simulations. Using additional Monte Carlo simulations and our analytical crowding model, we investigate the photometric accuracy which 30-m and 100-m ELTs will be able to achieve at distances extending to the Virgo cluster. We argue that for stellar populations work, ELTs will rapidly become crowding-limited, which suggests that low--Strehl AO systems might be sufficient for this type of science.
Based on research carried out at the National Optical Astronomy Observatory (NOAO) and the Gemini Observatory. NOAO is operated by the Association of Universities for Research in Astronomy Inc. (AURA), under a cooperative agreement with the National Science Foundation (NSF). The Gemini Observatory is operated by AURA under a cooperative agreement with the NSF on behalf of the Gemini partnership: the NSF (United States), the Particle Physics and Astronomy Research Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), CNPq (Brazil), and CONICET (Argentina).
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.