Space Interferometry Mission - Dynamical Observations of Galaxies (SIMDOG) Key Project

摘要

The Space Interferometry Mission (SIM) spacecraft will be used to measure the proper motions for a sample of ～30 nearby galaxies. At this time there are no proper motion measurements of galaxies beyond the satellite systems of the Milky Way. With the capability of measuring absolute positions to 4 μas (microarcsecond) accuracy and a five-year baseline, SIM will be able to measure proper motions as small as 10 km/s over the Local Group and 40 km/s at 4 Mpc. The motion of each galaxy will be monitored by targeting 5-10 stars that are brighter than 20th magnitude. SIM measurements will lead to knowledge of the full 6-dimensional position and velocity vectors of each galaxy. In conjunction with gravitational flow modeling, improved total mass measurements of individual galaxies and the fractional contribution of dark matter to galaxies of the Local Group will be obtained. The project includes development of theoretical methods for orbital calculations.