AAS 196th Meeting, June 2000
Session 31. NGST
Display, Tuesday, June 6, 2000, 10:00am-6:30pm, Empire Hall South

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[31.02] The effect of mid-frequency wavefront errors on NGST faint-galaxy photometry

M. A. Nieto-Santisteban, H. Ferguson, P. Bely (STScI), J. Trauger (JPL), A. Benson (University of Durham)

The performance of the Next Generation Space Telescope will be optimized at near-infrared wavelengths, however it is likely to have good sensitivity down to 0.6 microns. Image quality at these short wavelengths will come at a price, and it is important to quantify the effect of optical distortions on the ability to detect faint galaxies and measure their sizes and colors.

We have simulated 64 NGST images, 32 in the I band and 32 in the H band, by convolving NGST ideal images complete to magnitudes AB = 35 from a cosmological simulation with NGST model point-spread functions incorporating a wide range of low- and mid-frequency wavefront errors. Images were degraded with noise appropriate for 10-hour NGST exposures. The SExtractor galaxy photometry program was then used to detect galaxies in these images and measure their sizes and colors. We show how the detection efficiency, mean and rms photometric errors, and the uncertainties in galaxy size measurements vary with PSF parameters, and provide some simple figures of merit for assessing NGST optical performance.

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