Radiation Hydrodynamic Models and Simulated Observations of Radiative Feedback in Star Forming Regions
Thesis or dissertation
University of Exeter
This thesis details the development of the radiation transport code torus for radiation hydrodynamic applications and its subsequent use in investigating problems regarding radiative feedback. The code couples Monte Carlo photoionization with grid-based hydrodynamics and has the advantage that all of the features available to a dedicated radiation transport code are at its disposal in RHD applications. I discuss the development of the code, including the hydrodynamics scheme, the adaptive mesh refinement (AMR) framework and the coupling of radiation transport with hydrodynamics. Extensive testing of the resulting code is also presented. The main application involves the study of radiatively driven implosion (RDI), a mechanism where the expanding ionized region about a massive star impacts nearby clumps, potentially triggering star formation. Firstly I investigate the way in which the radiation field is treated, isolating the relative impacts of polychromatic and diffuse field radiation on the evolution of radiation hydrodynamic RDI models. I also produce synthetic SEDs, radio, Hα and forbidden line images of the bright rimmed clouds (BRCs) resulting from the RDI models, on which I perform standard diagnostics that are used by observers to obtain the cloud conditions. I test the accuracy of the diagnostics and show that considering the pressure difference between the neutral cloud and surrounding ionized layer can be used to infer whether or not RDI is occurring. Finally I use more synthetic observations to investigate the accuracy of molecular line diagnostics and the nature of line profiles of BRCs. I show that the previously unexplained lack of dominant blue-asymmetry (a blue-asymmetry is the expected signature of a collapsing cloud) in the line profiles of BRCs can be explained by the shell of material, swept up by the expanding ionized region, that drives into the cloud. The work in this thesis combines to help resolve the difficulties in understanding radiative feedback, which is a non–linear process that happens on small astrophysical timescales, by improving numerical models and the way in which they are compared with observations.
Haworth & Harries (2012), MNRAS, 420, 562
Haworth, Harries & Acreman (2012), MNRAS, 426, 203
Haworth, Harries, Acreman & Rundle (2013), MNRAS, 431, 3470
PhD in Physics
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Wu, Jin-Hui; Horsley, S.A.R.; Artoni, M.; La Rocca, G.C. (Nature Publishing Group, 2013)The typically tiny effect of radiation damping on a moving body can be amplified to a favorable extent by exploiting the sharp reflectivity slope at one edge of an optically induced stop-band in atoms loaded into an optical ...
Amundsen, David S.; Baraffe, I.; Tremblin, Pascal; Manners, James; Hayek, W.; Mayne, Nathan J.; Acreman, David M. (EDP Sciences for European Southern Observatory (ESO), 2014)The treatment of radiation transport in global circulation models (GCMs) is crucial to correctly describe Earth and exoplanet atmospheric dynamics processes. The two-stream approximation and correlated-k method are currently ...
Collapse of a molecular cloud core to stellar densities: stellar core and outflow formation in radiation magnetohydrodynamics simulations (Dataset) Bate, Matthew R.; Tricco, Terrence S.; Price, Daniel J. (University of Exeter (Data), 2013-10-10)This is the dataset that was used to produce the paper published in MNRAS. It contains the output from each of the SPH simulations, including dump files and the scripts used to generate the figures for the paper. To view ...