21 cm signal from cosmic dawn: Imprints of spin temperature fluctuations and peculiar velocities

Abstract

The 21 cm brightness temperature $\delta T_{\mathrm{b}}$ fluctuations from reionization promise to provide information on the physical processes during that epoch. We present a formalism for generating the $\delta T_{\mathrm{b}}$ distribution using dark matter simulations and an one-dimensional radiative transfer code. Our analysis is able to account for the spin temperature $T_{\mathrm{S}}$ fluctuations arising from inhomogeneous X-ray heating and Ly$\alpha$ coupling during cosmic dawn. The $\delta T_{\mathrm{b}}$ power spectrum amplitude at large scales ($k\sim 0.1$ Mpc${}^{-1}$) is maximum when $\sim 10\%$ of the gas (by volume) is heated above the CMB temperature. The power spectrum shows a "bump"-like feature during cosmic dawn and its location measures the typical sizes of heated regions. We find that the effect of peculiar velocities on the power spectrum is negligible at large scales for most part of the reionization history. During early stages (when the volume averaged ionization fraction $\lesssim 0.2$) this is because the signal is dominated by fluctuations in $T_{\mathrm{S}}$. For reionization models that are solely driven by stars within high mass ($\gtrsim 10^9{\mathrm{M}}_{\odot }$) haloes, the peculiar velocity effects are prominent only at smaller scales ($k\gtrsim 0.4$ Mpc${}^{-1}$) where patchiness in the neutral hydrogen density dominates the signal. The conclusions are unaffected by changes in the amplitude or steepness in the X-ray spectra of the sources.

23 pages, 21 figures, Accepted for publication in MNRAS. Added a section accounting for reionization sources in small haloes

References in corpus (24)

• Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Data Processing, Sky Maps, and Basic Results
• Cosmology at Low Frequencies: The 21 cm Transition and the High-Redshift Universe
• Efficient Simulations of Early Structure Formation and Reionization
• The observed ionization rate of the intergalactic medium and the ionizing emissivity at z >5: Evidence for a photon starved and extended epoch of reionization
• 21 cm fluctuations from inhomogeneous X-ray heating before reionization
• Foreground simulations for the LOFAR - Epoch of Reionization Experiment
• The CMBR fluctuations from HI perturbations prior to reionization
• Simulating Cosmic Reionization at Large Scales II: the 21-cm Emission Features and Statistical Signals
• Inside-out or Outside-in: The topology of reionization in the photon-starved regime suggested by Lyman-alpha forest data
• On using visibility correlations to probe the HI distribution from the dark ages to the present epoch I: Formalism and the expected signal
• Characterizing Foreground for redshifted 21-cm radiation: 150 MHz GMRT observations
• Cosmic Reionization and the 21-cm signal: Comparison between an analytical model and a simulation
• Fast Large-Scale Reionization Simulations
• The simulated 21 cm signal during the epoch of reionization : full modeling of the Ly-alpha pumping
• Lyman-alpha radiative transfer during the Epoch of Reionization: contribution to 21-cm signal fluctuations
• Time-evolution of ionization and heating around first stars and miniquasars
• Spin Exchange Rates in Electron-Hydrogen Collisions
• Redshifted 21 Centimeter Emission from Minihalos Before Reionization
• Nonlinear Bias of Cosmological Halo Formation in the Early Universe
• Spatially Extended 21 cm Signal from Strongly Clustered UV and X-Ray Sources in the Early Universe
• Radiative Transfer Effect on Ultraviolet Pumping of the 21cm Line in the High Redshift Universe
• The Spin-Resolved Atomic Velocity Distribution and 21-cm Line Profile of Dark-Age Gas
• Will Nonlinear Peculiar Velocity and Inhomogeneous Reionization Spoil 21cm Cosmology from the Epoch of Reionization?
• Measuring the Redshift of Reionization with a Modest Array of Low-Frequency Dipoles

Cited by in corpus (10)

• Improved upper limits on the 21-cm signal power spectrum of neutral hydrogen at $\mathbf{z}\approx 9.1$ from LOFAR
• Constraining the intergalactic medium at $z\approx$ 9.1 using LOFAR Epoch of Reionization observations
• Imaging the redshifted 21-cm pattern around the first sources during the cosmic dawn using the SKA
• Studying 21cm power spectrum with one-point statistics
• Models of the Cosmological 21 cm Signal from the Epoch of Reionization Calibrated with Lyman-alpha and CMB Data
• Deconvolving the Wedge: Maximum-Likelihood Power Spectra via Spherical-Wave Visibility Modeling
• Cosmological implications of the composite spectra of galactic X-ray binaries constructed using MAXI data
• 21-cm signatures of residual HI inside cosmic HII regions during reionization
• Line of sight anisotropies in the Cosmic Dawn and EoR 21-cm power spectrum
• Studying neutral hydrogen structures during the epoch of reionization using fractal dimensions