http://arxiv.org/abs/1810.12321
Spatial fluctuations in ultraviolet backgrounds can subtly modulate the distribution of extragalactic sources, a potential signal and systematic for large-scale structure surveys. While this modulation has been shown to be significant for 3D Ly-alpha forest surveys, its relevance for other large-scale structure probes has not been explored, despite being the only astrophysical process that likely can affect clustering measurements on greater than megaparsec scales. We estimate that background fluctuations, modulating the amount of HI, have a fractional effect of (0.03-0.3)(k/[10^(-2) Mpc^(-1)])^(-1) on the power spectrum of 21cm intensity maps at z=1-3. We find a somewhat smaller effect for H-alpha and Ly-alpha intensity mapping surveys of (0.001-0.1)(k/[10^(-2) Mpc^(-1)])^(-1) and even smaller effect for a more traditional survey that correlates the positions of individual H-alpha or Ly-alpha emitters. We also provide an estimate for the effect of backgrounds on low-redshift galaxy surveys in general based on a simple model in which ionizing background fluctuations modulate the rate halo gas cools, which then sources star formation: We estimate a maximum fractional effect on the power of ~0.01(k/[10^(-2) Mpc^(-1)])^(-1) at z=1. We compare the sizes of these imprints to cosmological parameter benchmarks for the next generation of redshift surveys: We find that ionizing backgrounds could results in a bias on the squeezed triangle non-Gaussianity parameter f_NL that can be larger than unity for power spectrum measurements with a SPHEREx-like galaxy survey, and typical values of intensity bias. Marginalizing over a shape of the form k^(-1) P_L, where P_L is the linear matter power spectrum, removes much of this bias at the cost of ~ 40% larger statistical errors.
P. Sanderbeck, V. Irsic, M. McQuinn, et. al.
Wed, 31 Oct 18
57/65
Comments: 13 pages, 8 figures, submitted to MNRAS
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