The PI and co-PI of this project will combine observational and theoretical efforts to understand how ordinary (baryonic) matter flows into and out of galaxies in different environments. The observational side of the project will focus on galaxies identified in the Sloan Digital Sky Survey (SDSS) with known star-forming properties that have quasars behind them. By obtaining spectra of the quasars and analyzing absorption lines due to once-ionized magnesium (Mg II) and neutral sodium (Na I) in the galaxies, they will determine the spatial extent of inflow or outflow signatures and whether they are correlated with star formation rate or environment. They will also analyze the Na I D line in lower luminosity galaxies, using spectra from the SDSS and DEEP2 surveys. The theoretical side of the project will use cosmological hydrodynamic simulations to calculate model profiles of the Mg and Na lines, in order to interpret the observations and identify signatures of "cold flow" accretion. The results from this study will inform the science justifications for, and implicitly the design of, next-generation ground-based telescopes. Also, the PI and co-PI, as instructors in the California State Summer School for Mathematics and Science, will develop a laboratory project using elements of their research for high-school students.
Intellectual Merit: We studied the formation of galaxies in a cosmological context using cosmological simulations and observations. Our aim was to understand how galaxies grow via gas accretion from the surrounding medium and how gas is recylced and enriched via feedback and star formation. We showed that a tell-tail signature of gas accretion into galaxies could be seen via absorption line studies. Specifically, absorption-line gas should be seen offset from the galaxy systemic velocity, but that it should generaally be co-rotating with the inner disk. We showed using observations that this is often the case. We further used observational studies of gas around the Milky Way galaxy to constrain the total baryonic content of our Galaxy's halo and demonstrated that current observaitons allow for the Galaxy's full allotment of baryons only if the hot gas profile is quite extended and low density. Future observations will be able to test this possibility. Broader Impacts: The PI taught each summer at the California State Summer School for Mathematics and Science at UC Irvine, a summer school for high-school students from all over the state referred to as COSMOS. Approximately 25 students and one local high school teacher spend a month each summer studying astronomy and astrophysics. They attend twelve hours of lecture a week on basica astronomy and take part in research projects guided by UCI faculty. The PI both lectured and acted as a research mentor during these summer sessions, and used simulation output files as part of the reseach plan. Further the PI gave approximately five public talks per year and host star parties at the UCI Observatory once a year. He made pro-bono appearances on science-based TV shows (Nat Geo, How the Univese Works, Through the Wormhole) talking about new scientific developments.
