Optimal survey parameters: Ly$\alpha$ and H$\alpha$ intensity mapping for synergy with the 21cm signal during reionization

Abstract

Intensity mapping of multiple emission lines is emerging as a new branch to astronomy, to probe both properties of ionizing sources and the medium between, in particular the intergalactic medium. For Epoch of Reionization (EoR) studies, both multi-line experiments and analysis methods are still in their infancy. Here we explore optimal survey parameters for Ly$\alpha$ (and H$\alpha$) intensity mapping up to high redshifts of reionization, and requirements for optimised synergy with 21cm experiments. We investigate line sensitivity, spectral resolution and detector pixel size requirements for optimal (high signal-to-noise) mission output. Power and cross-power spectra in a fiducial setup are derived, as are mock intensity maps. For line power spectrum measurements a cumulative signal-to-noise of O$\left(10^3\right)$, and for respective cross-spectra with SKA 21cm observations of O$\left(10\right)$ to O$\left(10^2\right)$ are possible per redshift bin around the midpoint of reionization. These high signal-to-noise tomographic measurements are in reach for line sensitivities $>8\times 10^{-18}$ergs${}^{-1}$sr${}^{-1}$Hz${}^{-1}$, spectral resolution $R>250$ and detector pixel sizes $<2$arcsec; all three requirements are met by the proposed Cosmic Dawn Intensity Mapper (CDIM). For CDIM similar S/N values are in reach for H$\alpha$. Already the planned NASA mission SPHEREx will detect during the EoR Ly$\alpha$ autopower and cross power with 21cm, for sensitivities better than $10^{-18}$ergs${}^{-1}$sr${}^{-1}$Hz${}^{-1}$ in a moderate 21cm foreground scenario (better than $10^{-17}$ergs${}^{-1}$sr${}^{-1}$Hz${}^{-1}$ in an optimistic scenario). We advocate for IR missions in flavor of CDIM for a leap in IM and finish by providing a cookbook for successful multi-line IM during the EoR.

12 pages, 6 (+2) figures. Figure 4 and 6 as well as section 6 present main conclusions. v2 adds prospects for measurements with HERA, as well appendices with background on IGM attenuation, auto-power spectra, and the Knox criterion for optimised errors

References in corpus (13)

• Efficient Simulations of Early Structure Formation and Reionization
• Observations of the Lyman-$\alpha$ Universe
• Cosmology with the SPHEREX All-Sky Spectral Survey
• First Season MWA EoR Power Spectrum Results at Redshift 7
• Detecting the Rise and Fall of 21 cm Fluctuations with the Murchison Widefield Array
• Intensity mapping of [CII] from early galaxies
• Dissecting the high-z interstellar medium through intensity mapping cross-correlations
• The Cross-Correlation of High-Redshift 21 cm and Galaxy Surveys
• Intensity mapping of H-alpha, H-beta, [OII] and [OIII] lines at z<5
• CDIM: Cosmic Dawn Intensity Mapper Final Report
• The spin-temperature dependence of the 21cm -- LAE cross-correlation
• Predictions for the 21cm-galaxy cross-power spectrum observable with SKA and future galaxy surveys
• Mind the gap: the power of combining photometric surveys with intensity mapping

Cited by in corpus (13)

• The THESAN project: predictions for multi-tracer line intensity mapping in the epoch of reionization
• LIMFAST. II. Line Intensity Mapping as a Probe of High-Redshift Galaxy Formation
• LIMFAST. I. A Semi-Numerical Tool for Line Intensity Mapping
• Probing Population III Initial Mass Functions with He II/H$\alpha$ Intensity Mapping
• Exploring the cosmic dawn and epoch of reionization with 21cm line
• Revisiting the [C II]${}_{158\mu \text{m}}$ line-intensity mapping power spectrum from the EoR using non-uniform line-luminosity scatter
• Detecting galaxy-21-cm cross-correlation during reionization
• Probing the Epoch of Reionization using synergies of line intensity mapping
• Field-level Reconstruction from Foreground-Contaminated 21-cm Maps
• The 21cm-galaxy cross-correlation: Realistic forecast for 21cm signal detection and reionisation constraints
• Revealing the formation histories of the first stars with the cosmic near-infrared background
• Radiative Transfer Simulations of Ly$\alpha$ Intensity Mapping During Cosmic Reionization Including Sources from Galaxies and the Intergalactic Medium
• A New Boundary Condition on Reionization