RUI: Reconstructing Galaxy Histories

University Of Hawaii At Hilo, Hilo HI

Investigators

Abstract

AST 0205960 West Understanding the origin and evolution of galaxies is one of the major goals of modern astrophysics. It is generally believed that galaxies arose from small density fluctuations in the primordial matter distribution that were amplified over time by gravity. However, our knowledge of the details of the galaxy formation process is still far from complete, and many important questions remain unanswered. How and when did galaxies form? How have they evolved over time? How do their environs influence galaxy properties? Over the past few years, Dr. Michael West has been pursuing a number of original lines of research, both observational and theoretical, to address these questions. With this award he will build upon previous successes and explore new avenues that may lead to further insights about the genesis of galaxies. Specific goals of this project include the following: o One of the most promising ways to learn the secrets of galaxy formation is by studying their globular cluster populations. Globular clusters are dense aggregates of up to a million stars that are held together by their mutual gravitational attraction. Most galaxies are surrounded by systems of tens, hundreds, or thousands of globular clusters that swarm around them like bees around a hive. The present-day globular populations of galaxies reflect the cumulative effects of billions of years of ongoing galaxy formation and evolution via mergers and collisions, accretion, generations of star formation, and other processes. Careful analysis of a galaxy's globular cluster population can thus allow astronomers to reconstruct its history. A major goal of Dr. West's project is to undertake the most comprehensive study yet of the globular cluster systems of hundreds of galaxies in the Virgo and Coma clusters. o Dr. West and collaborators recently found evidence of the existence of a sizeable population of intergalactic globular clusters that are not gravitationally bound to individual galaxies but instead roam freely throughout the cores of galaxy clusters. The discovery of this new class of objects is an exciting result that invites further study, and searches for intergalactic globulars in several nearby galaxy clusters are currently underway. The colors, luminosity function, and spatial and velocity distributions of these intergalactic globulars will place strong constraints on their origin. o A growing body of evidence suggests that galaxy destruction might be a much more common occurrence than previously thought, and that the births and deaths of galaxies are intertwined. Rich galaxy clusters are especially harsh environments, where small galaxies can be cannibalized by larger ones, collisions between galaxies can strip material from their halos, ablation removes their interstellar gas, and galaxies may be partially or even completely torn apart by tidal fields as they travel through the cluster core. Yet the demise of some galaxies may also give rise to new ones, as material spilled into intergalactic space is eventually recycled into other galaxies. A goal of this research project is to conduct the first systematic survey to look for the faint remains of disrupted galaxies in galaxy clusters, in order to place quantitative constraints on the current rate of galaxy destruction in dense environments. This award is made under the auspices of the Research at Undergraduate Institutions (RUI) program at the NSF. ***