http://arxiv.org/abs/1912.00828
Under the assumption that galaxies and Quasi-Stellar Objects (QSOs) dominate the metagalactic ultra-violet (UV) background, it is shown that at high redshifts fluctuations in the UV background are dominated by QSO shot noise and have an auto-correlation length of a few to several comoving Mpcs, depending on the bright end of the QSO luminosity function. The correlations create long range spatial coherence in the neutral hydrogen fraction. Using a semi-analytic model, it is demonstrated that the coherence may account for the broad distribution in effective optical depths measured in the Ly$\alpha$ forest spectra of background QSOs, for line-of-sight segments of comoving length $50h^{-1}$ Mpc at redshifts $5<z<6$. Capturing the fluctuations in a numerical simulation requires a comoving box size of $\sim1h^{-1}$ Gpc, although a box half this size may be adequate if sufficient random realizations of the QSO population are performed.
A. Meiksin
Tue, 3 Dec 19
64/90
Comments: 11 pages, 9 figures. Accepted for publication in MNRAS
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