University Of Arizona Astronomy

The University of Arizona in Tucson Arizona

Event:		"The Formation and Destruction of Star Clusters in (interacting) Galaxies"
Event Date/Time:		May 1, 2003 4:00 pm
Location:		Steward Observatory Room N210
Speaker:		Dr. Henny J.G.L.M. Lamers
Institution:		University of Utrecht, Astronomical Institute
Subject(s):		Steward/NOAO Colloquium
Contact:		Jill Bechtold email: jill@as.arizona.edu phone: 520-621-6533
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Event Description Posted: November 26, 2002 3:58 pm		<><><><><><><><><><><><><><><><><><><><><><><><><> NOAO/KPNO - NSO, DEPARTMENT OF ASTRONOMY AND STEWARD OBSERVATORY AND NRAO <><><><><><><><><><><><><><><><><><><><><><><><><> The University of Arizona JOINT COLLOQUIUM Prof. Henny J.G.L.M. Lamers Astronomical Institute and SRON Laboratory for Space Research Utrecht University / The Netherlands "THE FORMATION AND DESTRUCTION OF STAR CLUSTERS IN (INTERACTING) GALAXIES" Abstract: Star clusters are huge concentrations of stars. The oldest clusters in our galaxy are the globular clusters, which contain 10^5 to 10^7 stars. These clusters orbit the galaxy at distances up to 50 kpc. The youngest clusters are the open clusters containing 10^2 to 10^4 stars. They move only in the galactic plane. For many years astronomers have wondered whether these two types of clusters are formed in the same way or completely differently. Maybe the formation of star clusters was different in the past than it is now? Observations with the Hubble Space Telescope show that star clusters form in great quantities in interacting galaxies. For instance, the Antennae galaxies show thousands of young newly formed clusters. The collection of young star clusters in the Milky Way and in starburst galaxies show a powerlaw mass distribution, with N(M_cl) ~ M_cl^(-2.0). So the majority of the young clusters have a low mass. On the other hand, the collection of old globular clusters in the Galactic halo and in other galaxies show a Gaussian-like mass distribution which peaks around a few 105 Msun. In a recent study, based largely on HST observations of interacting galaxies, we have developed a new method for the determination of the cluster formation history and the destruction time of clusters. It turns out that the destruction time of star clusters in interacting galaxies is much shorter than in undisturbed galaxies. I will show HST-observations of clusters in several interacting galaxies and I will discuss how the clusters are formed and how they are destroyed. I will demonstrate and explain the new method for the determination of the cluster destruction times in different galaxies and discuss its consequences. By comparing the formation and destruction rates of star clusters in different galaxies, we can solve the puzzle of the formation of the old globular clusters. ----------------------------------------------------------- Thursday, May 1, 2003 4:00 p.m. Steward Observatory Lecture Hall - Room N210 Refreshments at 3:30PM in the Lobby