There is some conceptual overlap between this proposal and #189, "A First Look at Energy-Dependent Ionizing Escape", but the proposed analyses are completely different. The current proposal is more clearly about the galaxy-CGM-reionization connection while #189 is more clearly about galaxies, hence it may make sense to assign this proposal to a CGM TAC and #189 to a galaxies committee. In the unlikely event that both projects should be approved, I will adjust the planned workload and requested summer support accordingly. -1250431895 Assigned ID: 996 ----- Attempting Submission 1 (Sat Mar 07 00:22:14 GMT 2020) ----- I will study how observations of the physical impact that young galaxies had on their local environments test the hypothesis that galaxies dominated cosmological hydrogen reionization. A generation of deep HST-based surveys has now detected the first galaxies that emerged from the cosmic dark ages. Although these efforts offer a treasure-trove of insight into the early stages of galaxy formation, the extent to which the young galaxies actually ionized and heated their surroundings remains essentially unconstrained. Fortunately, the close spatial association between galaxies and their circumgalactic media suggests a simple test: if galaxies were bright ionizing sources, then fewer are expected around strong high-ionization metal absorbers such as triply-ionized carbon and silicon (CIV and SiIV). Conversely, if galaxies did not dominate reionization, then more are required to generate such an absorber. This new approach requires theoretical input: how many bright galaxies are expected near a strong absorber? How does this expectation depend on the absorber's properties and on assumptions regarding the galaxies' ionizing efficiency? In order to open up this field, I address these questions through the use of cosmological radiation-hydrodynamic simulations that self-consistently model both galaxy growth and reionization. In the process, I will reveal how existing and upcoming observations of the galaxy-absorber connection directly constrain the contribution that galaxies made to reionization. PI Dr. Kristian Finlator led all of the modifications to the Gadget-3 code baseline leading to the Technicolor Dawn simulations. He has published or supervised numerous theoretical inquiries into the high-redshift circumgalactic medium including four first-authored studies and two studies (one published, one submitted) led by a student under his supervision. Co-I Dr. Zheng Cai is an observational expert on high-redshift galaxy formation and extended line emission. He has extensive experience with HST. Among other contributions, he led an effort to use the HST narrowband ramp filter to identify Lyman-alpha emitters that may be associated with two strong high-redshift CIV absorbers. The graduate student who will work on this project will be selected based on interests and expertise. Intergalactic Medium and the Circumgalactic Medium Galaxies 0 Regular false false false true false SUPPORTED