On the Detectability of the Hydrogen 3-cm Fine Structure Line from the EoR
arXiv:0809.4279 · doi:10.1111/j.1365-2966.2008.13680.x
Abstract
A soft ultraviolet radiation field, 10.2 eV < E <13.6 eV, that permeates neutral intergalactic gas during the Epoch of Reionization (EoR) excites the 2p (directly) and 2s (indirectly) states of atomic hydrogen. Because the 2s state is metastable, the lifetime of atoms in this level is relatively long, which may cause the 2s state to be overpopulated relative to the 2p state. It has recently been proposed that for this reason, neutral intergalactic atomic hydrogen gas may be detected in absorption in its 3-cm fine-structure line (2s_1/2 -> 2p_3/2) against the Cosmic Microwave Background out to very high redshifts. In particular, the optical depth in the fine-structure line through neutral intergalactic gas surrounding bright quasars during the EoR may reach tau~1e-5. The resulting surface brightness temperature of tens of micro K (in absorption) may be detectable with existing radio telescopes. Motivated by this exciting proposal, we perform a detailed analysis of the transfer of Lyman beta,gamma,delta,... radiation, and re-analyze the detectability of the fine-structure line in neutral intergalactic gas surrounding high-redshift quasars. We find that proper radiative transfer modeling causes the fine-structure absorption signature to be reduced tremendously to tau< 1e-10. We therefore conclude that neutral intergalactic gas during the EoR cannot reveal its presence in the 3-cm fine-structure line to existing radio telescopes.
arXiv comment7 pages, 4 figures, MNRAS in press; v2. some typos fixed
References in corpus (18)
- Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
- Cosmology at Low Frequencies: The 21 cm Transition and the High-Redshift Universe
- Constraining the Evolution of the Ionizing Background and the Epoch of Reionization with z ~ 6 Quasars II: A Sample of 19 Quasars
- Measuring the Small-Scale Power Spectrum of Cosmic Density Fluctuations Through 21 cm Tomography Prior to the Epoch of Structure Formation
- Lyman Alpha Radiation From Collapsing Protogalaxies I: Characteristics of the Emergent Spectrum
- Wouthuysen-Field coupling strength and application to high-redshift 21 cm radiation
- Scattered Lyman-alpha Radiation Around Sources Before Cosmological Reionization
- Monte Carlo Simulation of Lyman Alpha Scattering and Application to Damped Lyman Alpha Systems
- Cosmic Hydrogen Was Significantly Neutral a Billion Years After the Big Bang
- Descending from on high: Lyman series cascades and spin-kinetic temperature coupling in the 21 cm line
- Evidence for a Cosmological Stromgren Surface and for Significant Neutral Hydrogen Surrounding the Quasar SDSS J1030+0524
- Quasar Proximity Zones and Patchy Reionization
- The Polarization of Scattered Lyman Alpha Radiation Around High-Redshift Galaxies
- A closer look at using quasar near-zones as a probe of neutral hydrogen in the intergalactic medium
- Radiative Transfer Effect on Ultraviolet Pumping of the 21cm Line in the High Redshift Universe
- The Fine Structure Lines of Hydrogen in HII Regions
- Hydrogen 2p--2s transition: signals from the epochs of recombination and reionization
- SKA Key science project: Radio observations of cosmic reionization and first light