scholarly journals The influence of metagalactic ultraviolet background fluctuations on the high-redshift Lyα forest

2019 ◽  
Vol 491 (4) ◽  
pp. 4884-4893 ◽  
Author(s):  
Avery Meiksin

ABSTRACT Under the assumption that galaxies and quasi-stellar objects (QSOs) dominate the metagalactic ultraviolet (UV) background, it is shown that at high redshifts, fluctuations in the UV background are dominated by QSO shot noise and have an autocorrelation 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 Lyα forest spectra of background QSOs, for line-of-sight segments of comoving length $50\, h^{-1}$ Mpc at redshifts 5 < z < 6. Capturing the fluctuations in a numerical simulation requires a comoving box size of ∼1 Gpc, although a box half this size may be adequate if sufficient random realizations of the QSO population are performed.

2006 ◽  
Vol 461 (1) ◽  
pp. 39-48 ◽  
Author(s):  
F. Fontanot ◽  
S. Cristiani ◽  
P. Monaco ◽  
M. Nonino ◽  
E. Vanzella ◽  
...  

1978 ◽  
Vol 224 ◽  
pp. 344 ◽  
Author(s):  
D. H. Roberts ◽  
G. R. Burbidge ◽  
A. H. Crowne ◽  
V. T. Junkkarinen ◽  
E. M. Burbidge ◽  
...  

1987 ◽  
Vol 314 ◽  
pp. 111 ◽  
Author(s):  
Scott F. Anderson ◽  
Bruce Margon

2020 ◽  
Vol 499 (2) ◽  
pp. 2401-2415
Author(s):  
A C Trapp ◽  
Steven R Furlanetto

ABSTRACT Cosmic variance is the intrinsic scatter in the number density of galaxies due to fluctuations in the large-scale dark matter density field. In this work, we present a simple analytic model of cosmic variance in the high-redshift Universe (z ∼ 5–15). We assume that galaxies grow according to the evolution of the halo mass function, which we allow to vary with large-scale environment. Our model produces a reasonable match to the observed ultraviolet (UV) luminosity functions in this era by regulating star formation through stellar feedback and assuming that the UV luminosity function is dominated by recent star formation. We find that cosmic variance in the UV luminosity function is dominated by the variance in the underlying dark matter halo population, and not by differences in halo accretion or the specifics of our stellar feedback model. We also find that cosmic variance dominates over Poisson noise for future high-z surveys except for the brightest sources or at very high redshifts (z ≳ 12). We provide a linear approximation of cosmic variance for a variety of redshifts, magnitudes, and survey areas through the public python package galcv. Finally, we introduce a new method for incorporating priors on cosmic variance into estimates of the galaxy luminosity function and demonstrate that it significantly improves constraints on that important observable.


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