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Cosmological Hydrodynamic Simulations with Suppressed Variance in the Ly alpha Forest Power Spectrum
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Number of Authors: 62019 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 871, no 2, article id 144Article in journal (Refereed) Published
Abstract [en]

We test a method to reduce unwanted sample variance when predicting Ly alpha forest power spectra from cosmological hydrodynamical simulations. Sample variance arises due to sparse sampling of modes on large scales and propagates to small scales through nonlinear gravitational evolution. To tackle this, we generate initial conditions in which the density perturbation amplitudes are fixed to the ensemble average power spectrum-and are generated in pairs with exactly opposite phases. We run 50 such simulations (25 pairs) and compare their performance against 50 standard simulations by measuring the Ly alpha 1D and 3D power spectra at redshifts z = 2, 3, and 4. Both ensembles use periodic boxes of 40 h(-1)Mpc containing 512(3) particles each of dark matter and gas. As a typical example of improvement, for wavenumbers k = 0.25 hMpc(-1) at z = 3, we find estimates of the 1D and 3D power spectra converge 34 and 12 times faster in a paired-fixed ensemble compared with a standard ensemble. We conclude that, by reducing the computational time required to achieve fixed accuracy on predicted power spectra, the method frees up resources for exploration of varying thermal and cosmological parameters-ultimately allowing the improved precision and accuracy of statistical inference.

Place, publisher, year, edition, pages
2019. Vol. 871, no 2, article id 144
Keywords [en]
early universe, intergalactic medium, methods: numerical
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:su:diva-166769DOI: 10.3847/1538-4357/aaf576ISI: 000457048700012OAI: oai:DiVA.org:su-166769DiVA, id: diva2:1295981
Available from: 2019-03-13 Created: 2019-03-13 Last updated: 2019-03-13Bibliographically approved

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Rogers, Keir K.
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Department of PhysicsThe Oskar Klein Centre for Cosmo Particle Physics (OKC)
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