Semi-numeric simulations of helium reionization and the fluctuating radiation background

Dixon, Keri L, Furnaletto, Steven R and Mesinger, Andrei (2014) Semi-numeric simulations of helium reionization and the fluctuating radiation background. Monthly Notices of the Royal Astronomical Society, 440. pp. 987-1001. ISSN 0035-8711

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Recent He II Lyman-alpha forest observations from 2.0 < z < 3.2 show large fluctuations in the optical depth at z > 2.7. These results point to a fluctuating He-ionizing background, which may be due to the end of helium reionization of this era. We present a fast, semi-numeric procedure to approximate detailed cosmological simulations. We compute the distribution of dark matter halos, ionization state of helium, and density field at z = 3 in broad agreement with recent simulations. Given our speed and flexibility, we investigate a range of ionizing source and active quasar prescriptions. Spanning a large area of parameter space, we find order-of-magnitude fluctuations in the He II ionization rate in the post-reionization regime. During reionization, the fluctuations are even stronger and develop a bimodal distribution, in contrast to semi-analytic models and the hydrogen equivalent. These distributions indicate a low-level ionizing background even at significant He II fractions.

Item Type: Article
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Subjects: Q Science > QB Astronomy
Depositing User: Jill Kirby
Date Deposited: 24 Jul 2014 14:01
Last Modified: 06 Mar 2017 23:34

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