Enhanced Detectability of Pre-reionization 21 cm Structure

  title={Enhanced Detectability of Pre-reionization 21 cm Structure},
  author={Marcelo A. Alvarez and Ue-li Pen and Tzu-Ching Chang},
  journal={The Astrophysical Journal},
Before the universe was reionized, it was likely that the spin temperature of intergalactic hydrogen was decoupled from the cosmic microwave background (CMB) by UV radiation from the first stars through the Wouthuysen-Field effect. If the intergalactic medium (IGM) had not yet been heated above the CMB temperature by that time, then the gas would appear in absorption relative to the CMB. Large, rare sources of X-rays could inject sufficient heat into the neutral IGM, so that ?Tb >0 at comoving… 

Figures from this paper

21-cm signature of the first sources in the Universe: prospects of detection with SKA
Currently several low-frequency experiments are being planned to study the nature of the first stars using the redshifted 21-cm signal from the cosmic dawn and epoch of reionization. Using a
The GMRT Epoch of Reionization experiment: a new upper limit on the neutral hydrogen power spectrum at z≈ 8.6
We present a new upper limit to the 21cm power spectrum during the Epoch of Reionization (EoR) which constrains reionization models with an unheated IGM. The GMRT-EoR experiment is an ongoing effort
Distinctive 21 cm structures of the first stars, galaxies, and quasars
Observations of the redshifted 21 cm line with upcoming radio telescopes promise to transform our understanding of the cosmic reionization. To unravel the underlying physical process, we investigate
Can the 21-cm signal probe Population III and II star formation?
Using varying models for the star formation rate (SFR) of Population (Pop) III and II stars at z>6 we derive the expected redshift history of the global 21 cm signal from the inter-galactic medium
Growth and anisotropy of ionization fronts near high-redshift quasars in the MassiveBlack simulation
We use radiative transfer to study the growth of ionized regions around the brightest, z=8 quasars in a large cosmological hydrodynamic simulation that includes black hole growth and feedback (the
Imaging the redshifted 21-cm pattern around the first sources during the cosmic dawn using the SKA
Understanding properties of the first sources in the Universe using the redshifted \HI ~21-cm signal is one of the major aims of present and upcoming low-frequency experiments. We investigate the
21 cm cosmology in the 21 st century
Imaging the Universe during the first hundreds of millions of years remains one of the exciting challenges facing modern cosmology. Observations of the redshifted 21 cm line of atomic hydrogen offer
Constraints on the redshift evolution of the LX–SFR relation from the cosmic X-ray backgrounds
Observations of local star forming galaxies have revealed a correlation between the rate at which galaxies form stars and their X-Ray luminosity. We combine this correlation with the most recent
21 cm signal from cosmic dawn: Imprints of spin temperature fluctuations and peculiar velocities
The 21 cm brightness temperature $\delta T_{\rm b}$ fluctuations from reionization promise to provide information on the physical processes during that epoch. We present a formalism for generating
21 cm cosmology in the 21st century.
This review detail the physics that governs the 21 cm signal and describe what might be learnt from upcoming observations, and generalize the discussion to intensity mapping of other atomic and molecular lines.


We investigate the 21 cm signature that may arise from the intergalactic medium (IGM) prior to the epoch of full reionization (z > 5). In scenarios in which the IGM is reionized by discrete sources
21-cm fluctuations from inhomogeneous X-ray heating before reionization
Many models of early structure formation predict a period of heating immediately preceding reionization, when X-rays raise the gas temperature above that of the cosmic microwave background. These
Probing beyond the epoch of hydrogen reionization with 21 centimeter radiation
We use numerical simulations of hydrogen reionization by stellar sources in the context of ΛCDM cosmogonies to investigate the 21 (1 + z) cm radio signal expected from the diffuse intergalactic
The 21 cm Background from the Cosmic Dark Ages: Minihalos and the Intergalactic Medium before Reionization
The H atoms inside minihalos (i.e., halos with virial temperatures Tvir ≤ 104 K, in the mass range roughly from 104 to 108 M☉) during the cosmic dark ages in a ΛCDM universe produce a redshifted
Constraining the unexplored period between the dark ages and reionization with observations of the global 21 cm signal
Observations of the frequency dependence of the global brightness temperature of the redshifted 21 cm line of neutral hydrogen may be possible with single dipole experiments. In this paper, we
The global 21-centimeter background from high redshifts
We consider the evolution of the sky-averaged 21-cm background during the early phases of structure formation. Using simple analytic models, we calculate the thermal and ionization histories,
Early reionization by miniquasars
Motivated by the recent detection by the Wilkinson Microwave Anisotropy Probe of a large optical depth to Thomson scattering, implying a very early reionization epoch, we assess a scenario where the
Heating of the intergalactic medium by primordial miniquasars
A simple analytical model is used to calculate the X-ray heating of the intergalactic medium (IGM) for a range of black hole masses. This process is efficient enough to decouple the spin temperature
The Growth of H II Regions During Reionization
Recently, there has been a great deal of interest in understanding the reionization of hydrogen in the intergalactic medium (IGM). One of the major outstanding questions is how this event proceeds on
Quasar H II Regions During Cosmic Reionization
Cosmic reionization progresses as HII regions form around sources of ionizing radiation. Their average size grows continuously until they percolate and complete reionization. We demonstrate how this