Extracting the astrophysics of reionization from the Ly$\alpha$ forest power spectrum: a first forecast

Abstract

The impact of cosmic reionization on the Ly$\alpha$ forest power spectrum has recently been shown to be significant even at low redshifts ($z\sim 2$). This memory of reionization survives cosmological time scales because high-entropy mean-density gas is heated to $\sim 3\times 10^4$ K by reionization, which is inhomogeneous, and subsequent shocks from denser regions. In the near future, the first measurements of the Ly$\alpha$ forest 3D power spectrum will be very likely achieved by upcoming observational efforts such as the Dark Energy Spectroscopic Instrument (DESI). In addition to abundant cosmological information, these observations have the potential to extract the astrophysics of reionization from the Ly$\alpha$ forest. We forecast, for the first time, the accuracy with which the measurements of Ly$\alpha$ forest 3D power spectrum can place constraints on the reionization parameters with DESI. Specifically, we demonstrate that the constraints on the ionization efficiency, $\zeta$, and the threshold mass for haloes that host ionizing sources, $m_{\mathrm{turn}}$, will have the $1\sigma$ error at the level of $\zeta =25.0\pm 11.6$ and ${\log }_{10}(m_{\mathrm{turn}}/{\mathrm{M}}_{\odot })=8.7_{-0.70}^{+0.36}$, respectively. The Ly$\alpha$ forest 3D power spectrum will thus provide an independent probe of reionization, probably even earlier in detection with DESI, with a sensitivity only slightly worse than the upcoming 21 cm power spectrum measurement with the Hydrogen Epoch of Reionization Array (HERA), i.e.\ ${\sigma }_{\mathrm{DESI}}/{\sigma }_{\mathrm{HERA}}\approx 1.5$ for $\zeta$ and ${\sigma }_{\mathrm{DESI}}/{\sigma }_{\mathrm{HERA}}\approx 2.0$ for ${\log }_{10}(m_{\mathrm{turn}}/$M${}_{\odot })$. Nevertheless, the Ly$\alpha$ forest constraint will be improved about three times tighter than the current constraint from reionization observations with high-z galaxy priors.

Updated to match accepted version for publication. 19 pages, 12 figures

References in corpus (12)

• The DESI Experiment Part I: Science,Targeting, and Survey Design
• Model-independent evidence in favor of an end to reionization by z~6
• Inferences on the Timeline of Reionization at z~8 From the KMOS Lens-Amplified Spectroscopic Survey
• Can the intergalactic medium cause a rapid drop in Lyman alpha emission at z>6?
• Constraining the neutral fraction of hydrogen in the IGM at redshift 7.5
• Dark energy and curvature from a future baryonic acoustic oscillation survey using the Lyman-alpha forest
• Luminosity Function from dedicated SDSS-III and MMT data of quasars in 0.7<z<4.0 selected with a new approach
• Scale-dependent bias in the BAO-scale intergalactic neutral hydrogen
• WEAVE-QSO: A Massive Intergalactic Medium Survey for the William Herschel Telescope
• Small-scale structure and the Lyman-$\alpha$ forest baryon acoustic oscillation feature
• Future Constraints on the Reionization History and the Ionizing Sources from Gamma-ray Burst Afterglows
• Impact of inhomogeneous reionization on the Lyman-α forest

Cited by in corpus (7)

• The Sherwood-Relics simulations: overview and impact of patchy reionization and pressure smoothing on the intergalactic medium
• Modeling the Lyman-$\alpha$ forest with Eulerian and SPH hydrodynamical methods
• Cosmic Reionization on Computers: Evolution of the Flux Power Spectrum
• Probing the cosmic web in Ly$\alpha$ emission over large scales: an Intensity Mapping forecast for DECaLS/BASS and DESI
• The long-lasting effect of X-ray preheating in the post-reionization intergalactic medium
• Separating the memory of reionization from cosmology in the Ly$\alpha$ forest power spectrum at the post-reionization era
• Reionization relics in the cross-correlation between the Ly$\alpha$ forest and 21 cm intensity mapping in the post-reionization era