Abstract
Spatial fluctuations in ultraviolet backgrounds can subtly modulate the distribution of extragalactic sources, a potential signal and systematic for largescale structure surveys. While this modulation has been shown to be significant for 3D Ly α forest surveys, its relevance for other largescale structure probes has been hardly explored, despite being the only astrophysical process that likely can affect clustering measurements on the scales of ≳Mpc. We estimate that the background fluctuations, modulating the amount of H i, have a fractional effect of (0.03–0.3) × (k/[10^{−2} Mpc^{−1}])^{−1} on the power spectrum of 21 cm intensity maps at z = 1–3. We find a smaller effect for H α and Ly α intensity mapping surveys of (0.001–0.1) × (k/[10^{−2} Mpc^{−1}])^{−1} and even smaller effect for more traditional surveys that correlate the positions of individual H α or Ly α emitters. We also estimate the effect of backgrounds on lowredshift galaxy surveys in general based on a simple model in which background fluctuations modulate the rate halo gas cools, modulating 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 sizes of these imprints to cosmological parameter benchmarks for the next generation of redshift surveys: We find that ionizing backgrounds could result in a bias on the squeezed triangle nonGaussianity parameter ƒ_{NL} that can be larger than unity for power spectrum measurements with a SPHERExlike 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 per cent larger statistical errors.
Original language  English 

Pages (fromto)  50595072 
Number of pages  14 
Journal  Monthly Notices of the Royal Astronomical Society 
Volume  485 
Issue number  4 
Early online date  14 Mar 2019 
DOIs  
Publication status  Published  Jun 2019 
Keywords
 cosmology: theory
 largescale structure of universe
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Avery Meiksin
 School of Physics and Astronomy  Personal Chair in Theoretical and Computational Physics
Person: Academic: Research Active