JANUARY 21 - 25, 2008

WEDNESDAY, JANUARY 23

12:30 pm: High Energy Astrophysics Division Lunch Talk. "The Active Nucleus of IC 4970: A Nearby Example of Merger-Induced Cold-Gas Accretion," Dr. Marie Machacek, CfA. Pratt Conference Room.

Abstract: Observations of nearby interacting galaxies in moderately massive groups offer a unique window into the dynamical processes that may trigger nuclear activity and promote the coevolution of black hole and host galaxy at earlier epochs, when galaxies were rapidly transforming. I will present results from Chandra X-ray and Spitzer mid-infrared observations of one such example, the interacting galaxy pair NGC6872/IC4970 in the Pavo galaxy group, that show the smaller companion galaxy IC4970 hosts a highly obscured active nucleus (AGN). I will use X-ray data to place limits on possible accretion modes for the AGN, and argue that nuclear activity in IC4970 is most likely triggered and fueled by cold gas driven into the nucleus during IC4970's ongoing off-axis encounter with the dust- and gas-rich spiral galaxy NGC6872.

THURSDAY, JANUARY 24

11:00 am: Institute for Theory and Computation (ITC) Colloquium. "Characterizing the ISM of High z Star-forming Galaxies with GRB Afterglow Spectroscopy," Jason X. Prochaska, University of California, Santa Cruz. Pratt Conference Room.

4:00 pm: Colloquium. "Crucial Dynamical Phases in Solar System Formation," Alessandro Morbidelli, Observatory of Nice, France. (Anyone wishing to meet with the speaker should contact the host, Prof. David Charbonneau, ext. 6-6515.) Preceded by tea at 3:30 pm. Phillips Auditorium.

Abstract: The formation and evolution of the giant planets of our Solar System presents several problems: the cores of the planets should have been driven into the Sun by Type I migration, faster than they could accrete their massive gaseous atmosphere; once formed, Jupiter and Saturn should have suffered Type-II migration towards the Sun, becoming hot or warm giants, like most of the extra-solar planets known so far; the planets most likely underwent a late reorganization of their orbital architecture, as indicated by the Late Heavy Bombardment (LHB) of the Moon, which suggests that a massive reservoir of small bodies suddenly became unstable. Without pretension of providing any definitive answer, I will present a scenario of the formation and evolution of the giant planets that addresses these problems. More specifically I will present simulations of the dynamics of planetary cores in the vicinity of a "planet trap," which can exist at the transition between the active and the dead zones of the disk. I will illustrate how the dynamics of the fully formed planets in the gas disk leads to one of 6 possible mutual configurations, that are stable and avoid significant migration towards the Sun. Finally I will describe our model for the origin of the LHB and how it connects with some of these mutual stable configurations.

SAO HUMAN RESOURCES NOTES

Leave Donations Requested

Due to a medical emergency, Joyce Janjigian of the Solar, Stellar and Planetary Science Division has been approved as a leave donor recipient in the Leave Transfer Program. Any SAO Trust Fund employee who wishes to donate annual leave to Joyce should complete a Leave Donor Form and send it to MS 17.

Under the Leave Transfer Program, Trust Fund employees may only donate annual leave to other Trust Fund employees and Federal employees may donate annual leave only to other Federal employees. If you should have any questions or are not able to access the form, please contact Anne LeBlanc, ext. 5-7371.

Job Vacancies

An online listing of all current SAO job openings is available. For more information, please call Human Resources, ext. 5-7371, or view your nearest bulletin board.