Date/Time
Date(s) - 06/02/2008
3:20 pm - 4:20 pm

Title: Measuring the Universe: Micro-arcsecond Astrometry with the VLBA

Speaker: Dr. Mark J. Reid

Institute: Harvard-Smithsonian – Center for Astrophysics

Location: ABB 102

Description:

Recently the Very Long Baseline Array (VLBA), an Earth-sized radio interferometer, has achieved trigonometric parallax and proper motion measurements with near micro-arcsecond accuracy. Major efforts are now underway to use the VLBA to measure distances to objects throughout the Milky Way and proper motions of other galaxies. This talk will present new results on parallaxes and proper motions of star forming regions, and the compact object at the center of the Milky Way. These measurements address fundamental problems in astrophysics, including evidence for supermassive black holes; the size, rotation speed, and mass of the Milky Way; and how massive star forming regions develop. While trigonometric parallaxes to other galaxies are currently beyond the reach of the VLBA, direct measurements of the angular rotation and proper motions of local group galaxies have been achieved. These measurements, combined with theoretical calculations, constrain the dark matter content and angular momentum in the Local Group. Finally, progress has been made in theattempt to measure the Hubble constant (Ho) directly and with high accuracy, by observing water masers in AGN accretion disks associated with galaxies in the Hubble flow.