Small-scale structure and the Lyman- forest baryon acoustic oscillation feature
arXiv:1707.03358 · doi:10.1093/mnras/stx2854
Abstract
The baryon-acoustic oscillation (BAO) feature in the Lyman- forest is one of the key probes of the cosmic expansion rate at redshifts z~2.5, well before dark energy is believed to have become dynamically significant. A key advantage of the BAO as a standard ruler is that it is a sharp feature and hence is more robust against broadband systematic effects than other cosmological probes. However, if the Lyman- forest transmission is sensitive to the initial streaming velocity of the baryons relative to the dark matter, then the BAO peak position can be shifted. Here we investigate this sensitivity using a suite of hydrodynamic simulations of small regions of the intergalactic medium with a range of box sizes and physics assumptions; each simulation starts from initial conditions at the kinematic decoupling era (z~1059), undergoes a discrete change from neutral gas to ionized gas thermal evolution at reionization (z~8), and is finally processed into a Lyman- forest transmitted flux cube. Streaming velocities suppress small-scale structure, leading to less violent relaxation after reionization. The changes in the gas distribution and temperature-density relation at low redshift are more subtle, due to the convergent temperature evolution in the ionized phase. The change in the BAO scale is estimated to be of the order of 0.12% at z=2.5; some of the major uncertainties and avenues for future improvement are discussed. The predicted streaming velocity shift would be a subdominant but not negligible effect (of order ) for the upcoming DESI Lyman- forest survey, and exceeds the cosmic variance floor. It is hoped that this study will motivate additional theoretical work on the magnitude of the BAO shift, both in the Lyman- forest and in other tracers of large-scale structure.
21 pages, 8 figures, matches MNRAS accepted version
References in corpus (19)
- The DESI Experiment Part I: Science,Targeting, and Survey Design
- Wide-Field InfrarRed Survey Telescope-Astrophysics Focused Telescope Assets WFIRST-AFTA 2015 Report
- Baryon Acoustic Oscillations in the Lyα forest of BOSS DR11 quasars
- Baryon Acoustic Oscillations in the Ly-α forest of BOSS quasars
- The Cosmic Linear Anisotropy Solving System (CLASS) I: Overview
- Evidence of patchy hydrogen reionization from an extreme Ly trough below redshift six
- Baryon acoustic oscillations from the complete SDSS-III Ly-quasar cross-correlation function at
- Keeping the Universe ionised: Photo-heating and the clumping factor of the high-redshift intergalactic medium
- Canadian Hydrogen Intensity Mapping Experiment (CHIME) Pathfinder
- Minihalo photoevaporation during cosmic reionization: evaporation times and photon consumption rates
- An improved measurement of the flux distribution of the Ly-alpha forest in QSO absorption spectra: the effect of continuum fitting, metal contamination and noise properties
- Imprint of Inhomogeneous Hydrogen Reionization on the Temperature Distribution of the Intergalactic Medium
- Results from EDGES High-Band: I. Constraints on Phenomenological Models for the Global cm Signal
- Lyman-alpha Forest Tomography from Background Galaxies: The First Megaparsec-Resolution Large-Scale Structure Map at z>2
- The formation and gas content of high redshift galaxies and minihalos
- On the signature of the baryon-dark matter relative velocity in the two and three-point galaxy correlation functions
- On Modeling and Measuring the Temperature of the z~5 IGM
- Redshifted 21 Centimeter Emission from Minihalos Before Reionization
- Probing the Epoch of Reionization with the Lyman Alpha Forest at z~4-5