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Title
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The impact of different physical processes on the statistics of Lyman-limit and damped Lyman absorbers
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Author
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Abstract
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| We compute the z = 3 neutral hydrogen column density distribution function f(N-Hi) for 19 simulations drawn from the Overwhelmingly Large Simulations project using a post-processing correction for self-shielding calculated with full radiative transfer of the ionizing background radiation. We investigate how different physical processes and parameters affect the abundance of Lyman-limit systems (LLSs) and damped Lyman alpha absorbers including: (i) metal-line cooling; (ii) the efficiency of feedback from supernovae and active galactic nuclei; (iii) the effective equation of state for the interstellar medium; (iv) cosmological parameters; (v) the assumed star formation law and (vi) the timing of hydrogen reionization. We find that the normalization and slope, D = d log(10) f/d log(10) N-H1, of f(N-Hi) in the LLS regime are robust to changes in these physical processes. Among physically plausible models, f(N-Hi) varies by less than 0.2 dex and D varies by less than 0.18 for LLSs. This is primarily due to the fact that these uncertain physical processes mostly affect star-forming gas which contributes less than 10 per cent to f(N-Hi) in the LLS column density range. At higher column densities, variations in f(N-Hi) become larger (approximately 0.5 dex at f(N-Hi) = 10(22) cm(-2) and 1.0 dex at f(N-Hi) = 10(22) cm(-2)) and molecular hydrogen formation also becomes important. Many of these changes can be explained in the context of self-regulated star formation in which the amount of star-forming gas in a galaxy will adjust such that outflows driven by feedback balance inflows due to accretion. Tools to reproduce all figures in this work can be found at the following url: https://bitbucket.org/galtay/hi-cddf-owls-1. |
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Language
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English
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Source (journal)
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Monthly notices of the Royal Astronomical Society. - Oxford, 1983, currens
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Publication
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Oxford
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2013
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ISSN
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0035-8711
[print]
1365-2966
[online]
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DOI
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10.1093/MNRAS/STT1765
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Volume/pages
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436
:3
(2013)
, p. 2689-2707
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ISI
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000327540000059
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Full text (Publisher's DOI)
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