RUI: Galaxy Construction and Destruction

University Of Hawaii, Honolulu

Investigators

Abstract

AST-0071149 WEST The genesis of galaxies is one of the great outstanding problems in modern astrophysics. How and when did galaxies form? How have the galaxies evolved over time? How does environment influence galaxy properties? One way to unravel the secrets of galaxy formation is by studying their globular cluster systems. Globular clusters are dense aggregates of up to a million stars that are found in the halos of most galaxies. They are believed to be among the oldest stellar ensembles in the universe, most likely predating the formation of their parent galaxies. As such, these fossil remains from the early universe may provide important clues about the birth of galaxies. Once galaxies have formed, they are subject to collisions, mergers, and partial or even total destruction from interactions with other galaxies. For example, large galaxies may grow by devouring smaller galaxy companions in an act of galactic cannibalism. Furthermore, material torn from galaxies during collisions may eventually be incorporated into other new or existing galaxies, a sort of recycling on cosmic scales. The birth and death of galaxies thus appear to be interwoven. Over the past few years, astronomers have been pursuing a number of original lines of research, both observational and theoretical, to understand the construction and destruction of galaxies. The goals of this research project are to continue and expand upon previous successes. Specific goals of this research project are: To analyze the globular cluster metallicity distributions in a large sample of galaxies in order to place quantitative constraints on the previous merger histories of these galaxies. Using a recently adapted modeling technique, it is now possible to determine what fraction of the present-day luminosity of a galaxy has been inherited from other galaxies via mergers and/or accretion of tidally stripped material. It is now possible to determine more precisely how of this sort of merging has occurred, using globular clusters as a diagnostic. To search for an expected population of intergalactic globular clusters which do not belong to any particular galaxy, but rather roam freely throughout the cores of rich galaxy clusters such as Virgo and Coma. Such a population of intergalactic globular clusters must surely exist, a consequence of galaxy tidal interactions, which remove stars and globular clusters and spread them throughout intergalactic space. This goal of the project is to search for this expected population of intergalactic globular clusters using data from major ground-based observatories and upcoming Hubble Space Telescope observations. An ongoing wide-field, multi-color imaging survey of the Coma cluster of galaxies, the most ambitious cluster survey ever undertaken, will be continued. Among the goals are to provide a definitive measurement of the luminosity function of the Coma cluster galaxies, and to search for the faint remains of galaxies, which have been tidally disrupted by their passage through Coma's core. This survey will provide an extremely rich database that can be used for many years. The research program will involve a number of collaborators at different universities and will include undergraduate astronomy students at the University of Hawaii at Hilo. This project is funded by the Division of Astronomical Sciences. ***