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Paper: The Confusion Limit on Astrometry with SIM
Volume: 194, Working on the Fringe: Optical and IR Interferometry from Ground and Space
Page: 147
Authors: Rajagopal, J.; Allen, R. J.; Böker, T.
Abstract: An important "floor" requirement for the Space Interferometry Mission (SIM) is to carry out precision astrometry in crowded fields. This capability will be required, to name just two cases, to measure proper motions of stars in the disks of nearby spiral galaxies en-route to acquiring distance estimates through "rotational parallax" and in exploring the dynamics of these galaxies. In this poster we look at the errors introduced by confusion, i.e, the presence of objects other than the targetted star in the SIM field of view, in crowded-field astrometry. Using existing images of nearby galaxy disks (primarily M31) we attempt to simulate the background in a typical SIM FOV and estimate the errors in the measured position of a typical target star. The errors introduced because of pointing offsets (of particular importance in proper motion studies where a field has to be revisited) are also studied.
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