Collaborative Research: The Circumgalactic Medium: Understanding Observations from Theory

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Precisely how galaxies initially form and how they change throughout their lifetimes are among the least understood problems in astrophysics, and understanding the formation and life cycle of galaxies is key to developing the broadest astronomical perspective on how the Universe evolved to its present state. Many projects are centered on unraveling these mysteries. This project is focused on understanding the circumgalactic medium (CGM) to uncover its role in the life cycle of galaxies.PI Churchill will expand his previous Broader Impact program based upon his course "Into the Final Frontier." This course links students to Space Port America and the growing aerospace and tourism industry rapidly growing in Las Cruces, New Mexico. Special emphasis is placed on forging STEM related opportunities for minority students, which comprise 45% of New Mexico State's student population. Two graduate students will be supported in New Mexico. PI Charlton plans to transform her successful science fiction, interactive, web astronomy course into a video game to teach K--12 students, while achieving STEM astronomy standards for the state of Pennsylvania. This project will support two pre-selected skilled and talented students to construct the game and integrate it into local schools. One graduate student will be supported in Pennsylvania.The CGM is understood through observations and analysis of absorption lines in the spectra of quasars. However, being blind to the actual properties of the absorbing gas, present day analysis methods are uncalibrated. That is, our cumulative knowledge of the CGM and its role in galaxy evolution is based upon a host of implicit and explicit assumptions that remain untested or quantified. Using the Eulerian hydrodynamic N-body cosmological simulation code hydroART, the team will use the quasar absorption line technique, coupled with direct analysis of the simulations, to study highly-detailed simulated galaxies with various star formation and feedback physical models. The galaxies will range in viral halo mass from 10.5 log(M/Msun) 12.5 and in redshift from z ~ 0-3. The team aims to address these questions: (1) What is the relationship between the gas phase structures in and surrounding galaxies and the physical model for star formation and stellar feedback? (2) How well do models that yield galaxies matching global galaxy properties also match the observed properties of the gaseous reservoirs? (3) How does the CGM regulate the baryon cycle and galaxy evolution? (4) Do current analysis methods of absorption lines yield inferred gas properties (metallicities, spatial-kinematics distributions, gas phases, and gas reservoir masses) that are consistent with the gas being probed in the simulations? (5) What are the quantitative relationships between inferred gas properties from observational analysis and the gas actually giving rise to the absorption? (6) What are the implications and how do they change our understanding of the baryon cycle and galaxy evolution?