Most galaxies in the Universe, including our own Milky Way, are members of poor groups. Previous optical studies of X-ray selected groups have revealed strong correlations between the global group properties and the presence or absence of X-ray emission, but those samples were biased towards X-ray luminous systems. This project is the first detailed optical and X-ray study of an unbiased sample of nearby, ideally more typical, groups. The 25-member sample has been carefully selected to be representative of groups in general. Each group is being observed with the Inamori-Magellan Areal Camera and Spectrograph (IMACS) wide-field multi-object spectrograph on the Magellan I telescope in Chile, in order to determine group membership, derive the star formation properties of group galaxies, estimate the fraction of active galactic nuclei, determine the luminosity function, and calculate global kinematic properties. Each group is also being observed by the X-ray Multi-Mirror (XMM-Newton) satellite to determine the properties of the hot intra-group medium. Combining these complementary observations will allow a complete census of the properties of nearby groups, for comparison to existing high-redshift samples, to study how the properties of group galaxies evolve in time.
The data obtained by this research will be incorporated into the Discovery Project. This innovative educational resource created by the principal investigator comprises the creation of a classroom dedicated solely to science, and a web-based curriculum using the many existing astronomy-based educational activities. . The goal of the Discovery Project is to inspire academically challenged students to understand the role of science in their life. The research will directly involve undergraduate students, targeting traditionally under-represented groups, as has been done effectively before. The researcher is also the primary scientific driver for Carnegie's new public lecture series, and will be adding pre-lecture talks for elementary and middle school students to the main lecture intended for adults.
Most galaxies (including our own Milky Way galaxy) occur not in isolation but in small collections of galaxies called galaxy groups. This NSF program was designed to better understand what impact being a member of a galaxy group has on a galaxy. To address this question, we observed a large sample of nearby galaxy groups with the Magellan telescopes in Las Campanas, Chile. We also observed these groups with the XMM-Newton X-ray telescope, the Spitzer infrared telescope and the Hubble Space Telescope. Using this data, we compared the properties of galaxies in the group to galaxies in isolation. Our study conclusively showed for the first time that the group environment has a big impact on the properties of galaxies. For example, we find that galaxies in groups are forming stars at a much lower rate than galaxies in isolation. This suggests that the group environment suppresses star formation. Although there are many possible reasons, we believe it is most likely the interaction of galaxies with the hot gas in the group that leads to this suppression. However, in a small number of systems, star formation is enhanced. This tends to occur when two galaxies merge to form a single system. Our project suggests that this is the ultimate fate of the Milky Way galaxy: it will eventually merge with the nearby Andromeda system. Most of the work for this project was carried-out by two undergraduate students and two postdoctoral associates. Results from this project were presented by the PI at several public lectures in the years 2009, 2010 and 2011. Several of these lectures were held concurrently with star parties at elementary and middle schools throughout southern California. During these events, the PI brings telescopes to schools allowing school children and their families to view celestial objects and ask questions about the Universe.
