"Fragmentation in Primordial Gas: Improving H2 Cooling and Self-Shielding"
Primordial star formation is an important field of current research, because the properties of these first stars influence the chemical enrichment, turbulent mixing, and reionisation of the primordial gas. Therefore, they define the initial conditions for subsequent star and galaxy formation.
Molecular hydrogen (H2) is the dominant coolant in primordial gas. When the H2 lines become optically thick at high densities, we need a special numerical treatment in order to model H2 cooling accurately. In order to do so, we implement a new method for the determination of effective column densities in the SPH code Gadget2. A comparison to commonly used local, isotropic methods (Sobolev, Gnedin, analytical fits) shows that these local approaches generally underestimate the photon escape fraction, because they miss the flattening of the cloud.
I will present our new method, show how it promotes fragmentation in primordial gas and discuss improvements for the commonly used local methods. Moreover, I explain how this new method can be applied to the determination of effective column densities in order to model H2 self-shielding against photodissociation in protogalactic gas clouds more accurately.
University of Heidelberg, Germany
(host: Volker Bromm)
PhD Defense Presentation
"Simulating the Formation, Properties, and Impact of Stellar Systems in the First Galaxies"
University of Texas at Austin
PhD Committee Meeting follows at 12 Noon in RLM 15.216A