Collaborative Research: An Archaeological Survey for Substructure in the Stellar Halos of the Nearest Massive Galaxies

University Of California-Santa Cruz, Santa Cruz CA

Investigators

Abstract

Our Milky Way galaxy is surrounded by "dwarf" galaxies that orbit and occasionally collide with our galaxy. We are part of a "local group" of large galaxies, each with its own swarm of dwarf galaxies. One of the important unanswered questions in astronomy is how these galaxies formed and how they change in time. Our current understanding of structure in the universe suggests that a large galaxy like the Milky Way should actually host a larger number of dwarf satellites than we observe. To examine whether this is universal or merely a property of our local group, this program will conduct a detailed census of the regions surrounding two of our nearest galactic neighbors. They will survey two types of galaxy - spiral, like the Milky Way, and a large elliptical galaxy - and then measure the basic properties of these newly discovered systems. This involves a collaborative effort between three institutions and will use some of the largest and best ground-based telescopes. All three PIs are active in education and public outreach. PI Sand's institution, Texas Tech University, has a new astrophysics research group and undergraduate concentration. The science in this proposal will help establish TTU's astrophysics program and reach out to the larger Lubbock community. In particular, two undergraduate astrophysics students will spend summers in California doing research for the program, allowing them to interact with the larger astrophysics community. PI Guhathakurta is very actively involved with several programs that provide mentoring and research experiences for high-school students. The three PIs, along with a postdoctoral researcher and students, will address the observed lack of faint dwarf galaxies associated with the Milky Way and M31 (compared Lambda-CDM predictions for small-scale structure formation). Using the Magellan and Keck telescopes, they will conduct a panoramic imaging study to measure the stellar stream and dwarf galaxy content in NGC 253, a Milky Way-like spiral in a filamentary environment, and NGC 5128, a massive central elliptical galaxy. They will also use Keck+Diemos and newly-developed coaddition techniques to obtain spectra of tidal streams and dwarf galaxies. If successful, this would enable kinematic and metallicity studies for the first time outside the local group.