Collaborative Research: The First Galaxies and their Stellar Populations

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AST-1109243/1109008Norman/ReynoldsAdaptive mesh refinement cosmological radiation hydrodynamic simulations pioneered by this group have recently expanded to include sufficient physics and enough resolution to simulate directly the prior effects of Population III star-forming mini-halos on the first galaxies. This technical advance has occurred just when observations from both ground and space are providing astrophysical data on galaxies in the previously unimaginable range of redshifts from 6 to 8.5. These observations indicate substantial evolution in the bright end of the luminosity function, and a steep faint end slope consistent with the notion that high-redshift dwarfs dominate the reionization photon budget. They also reveal substantial evolution in stellar populations over this redshift interval. The advance in simulation capability is also well timed for the start of operations of the first NSF-supported sustained petaflops supercomputer, Blue Waters.Combining these software, hardware, and data advances, this project will simulate the formation and evolution of the first galaxies across the entire range of masses and luminosities observed, and compare the results to the data through simulated images and spectra. This will lead to inferences about the Population III initial mass function, feedback effects, the growth of supermassive black holes, and even the dark matter power spectrum, and place important constraints on the accretion rate of gas onto galaxies. The simulations will improve estimates of the escape of ionizing radiation into the intergalactic medium, and directly address whether high-redshift galaxies are capable of reionizing the Universe. This is the very first time such near-first-principles simulations are feasible, due to the convergence of petascale computing hardware, simulation software, and algorithmic advances, and also the first time that relevant observational constraints are being obtained.Simulations at this scale have a strong impact on the astronomical community, the high performance computing community, and the larger science and technology-curious public. They drive the development of the hardware, software, and networking infrastructure. This project is one of six selected for first access to NSF's new petascale supercomputer, and the required code enhancements will be made generally available. There are also plans to include these scientific results in a new IMAX film by the Reuben H.Fleet Science Museum in Balboa Park, San Diego, anticipated in 2013.