Reconstructing The Cosmic Density Field to Understand the Local Intergalactic Medium and its Relation to Galaxies

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Dr. Mo and his team will use the Sloan Digital Sky Survey (SDSS), a large survey of nearby galaxies, to reconstruct the distribution of dark matter in the local Universe at the present time. With the aid of large gravitational N-body simulations, they will deduce what that matter distribution must have been earlier in cosmic history, before the galaxies began to form their stars. At those early times, normal matter in the form of gas would have been evenly mixed with the dark matter. The team will then use smooth-particle hydrodynamic simulations to follow the combined development of the dark matter and the gas, under various assumptions about how the gas is turned into stars, and how those stars feed energy back into the intergalactic gas. Their aims include testing a currently-popular model, according to which gas is shocked and heated as it falls into massive systems, but flows quietly into smaller galaxies, remaining cold so that it can readily form stars. They will estimate how much gas is associated with various cosmic environments, such as filaments and sheets of galaxies, and examine how metals produced by the nuclear reactions inside stars are fed into the intergalactic gas.A graduate student will be trained by participating in the research, and the team also expects to offer small-scale research projects for undergraduates. The density fields derived from the SDSS catalog, and various catalogs from the simulations, will be made available to the astronomical community. The team will produce three-dimensional maps of the reconstructed distribution of dark matter, luminous galaxies and intergalactic gas, for use in teaching and public outreach.