In recent years, diffraction-limited infrared observations with the world's largest infrared telescopes have yielded many of the most exciting and important breakthroughs in the study of the center of our Galaxy. Drs. Andrea Ghez and Mark Morris (University of California - Los Angeles) will conduct a five-year program of Galactic center research which has three primary objectives: 1) Obtain a precision measurement of the Galaxy's central gravitational potential with stellar orbits. This will provide a value of the distance to the Galactic Center to better than one percent accuracy and give a limit or a value for the mass of a black hole companion to the super-massive black hole (SMBH) at the Galactic Center. These determinations are preliminary to, and essential for, this program's long-term investigation of general relativistic effects in the strong gravity regime and of the extended dark matter distribution that has been proposed to exist there, 2) Use stellar dynamics to discriminate between theories attempting to account for the puzzling presence of young stars near the SMBH. This will include the first measurements of eccentricities for stars thought to reside in the stellar disk recently discovered in the central parsec, without the a priori assumption of disk membership. Similar measurements will also provide strong constraints, or measurement, of any intermediate-mass black holes at the center of the massive young star cluster, the Arches, and 3) Measure the distribution of old stars in the dynamically relaxed stellar cusp centered on the SMBH in order to test models of stellar dynamics and of nuclear SMBH growth. The conclusions drawn from the research described in this proposal can, in most cases, be applied to other spiral galaxies as well, thereby elucidating the evolution of their central SMBHs, and the interplay of those SMBHs with the formation, dynamics and fate of their surrounding stars.
One important aspect of this project is in demonstrating the power of laser guide star adaptive optics (LGSAO), which has only recently been implemented on 8 to 10 meter-class telescopes. While this technology is a key component of future large ground-based telescopes, it has yet to be fully accepted by the astronomical community. Furthermore, aspects of the proposed work will inform the design and operation of future LGSAO systems. In terms of education, the team will widely disseminate their results on our Galaxy's SMBH and its surroundings, which have tremendous appeal to the general public, by creating publically-available material for undergraduate textbooks and course material, documentaries, and museum exhibits and giving public talks. They will also continue to train and mentor a large number of underrepresented minorities, particularly women, who are attracted to working on this program by its success and the commitment of Dr. Ghez to encouraging young women into science.
