What are the kinematics of the Galaxy and the Local Group?
It is now possible to measure proper motions of masers in a very few members of the Local Group of galaxies. With longer time baselines, it will be possible to measure more, allowing distance measurements and orbit determinations. This will provide key parameters for measuring the mass content and distribution in the Local Group. Within the Galaxy, proper motion and parallax measurements of masers and pulsars will help refine knowledge of the structure and kinematics of the galaxy. The improved understanding of the distribution of dark matter in the Local Group would have much broader cosmological implications. • Gravitational lenses – Where is the dark matter? Studies of the structure of lensed sources at high resolution can yield strong constraints on the distribution and substructure of dark matter in galaxies. Also, increased sensitivity will allow detection of weak central components expected in lenses, which will constrain the mass distribution close to the centers of lensing gal
