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Title: Radiative feedback and the first stars
Author: Glover, Simon
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2002
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Numerical simulations suggest that the very first stars to form do so within cool gas in small protogalaxies. These protogalaxies have low virial temperatures, and cooling within them is dominated by molecular hydrogen, H2. This is easily destroyed by ultraviolet radiation from newly-formed stars, and this ‘radiative feedback’ may play an important role in regulating star formation in the early universe. To study the effects of radiative feedback, requires an accurate chemical model. examples currently in the literature . In chapter 2 I develop a chemical model that correctly treats the photochemistry of optically thick primordial gas. I also discuss the approximations that remain, and estimate the accuracy of the model. In chapter 3, I examine the role of radiative feedback on small scales. Using a simple protogalactic model, I determine the growth timescales and final sizes of H II regions within a protogalaxy and discuss the effect of photoionizing radiation on dense clumps of gas. I also examine the effects of photodissociation, and present a simple method for estimating the photodissociation timescales in optically thick gas. I find that radiative feedback occurs rapidly in diffuse protogalactic gas, but that dense clumps can resist its effects and survive to form stars. In chapter 4, I examine the importance of these X-rays by self-consistently modelling the growth of the X-ray and UV backgrounds together with the effects on gas within protogalaxies. An important result is the determination of Tcrit is presented for various X-ray source models, and compared to a model with no X-ray background, allowing the effects of X-ray feedback to be assessed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available