The 21-cm Background from the Cosmic Dark Ages: Minihalos and the Intergalactic Medium before Reionization

Abstract

The H atoms inside minihalos (i.e. halos with virial temperatures T_vir < 10^4 K, in the mass range roughly from 10^4 M_sun to 10^8 M_sun) during the cosmic dark ages in a LCDM universe produce a redshifted background of collisionally-pumped 21-cm line radiation which can be seen in emission relative to the cosmic microwave background (CMB). Previously, we used semi-analytical calculations of the 21-cm signal from individual halos of different mass and redshift and the evolving mass function of minihalos to predict the mean brightness temperature of this 21-cm background and its angular fluctuations. Here we use high-resolution cosmological N-body and hydrodynamic simulations of structure formation at high redshift (z > 8) to compute the mean brightness temperature of this background from both minihalos and the intergalactic medium (IGM) prior to the onset of Ly-alpha radiative pumping. We find that the 21-cm signal from gas in collapsed, virialized minihalos dominates over that from the diffuse shocked gas in the IGM.

arXiv comment8 pages, 5 figures. To appear in proceedings of UC Irvine May 2005 workshop on "First Light & Reionization", eds. E. Barton & A. Cooray, New Astronomy Reviews, in press

References in corpus (4)

• On the Direct Detectability of the Cosmic Dark Ages: 21-cm Emission from Minihalos
• Nonlinear clustering during the cosmic Dark Ages and its effect on the 21-cm background from minihalos
• The Postcollapse Equilibrium Structure of Cosmological Haloes in a Low-Density Universe
• Large-Scale Structure Shocks at Low and High Redshifts

Cited by in corpus (6)

• Observational constraints on Cosmic Reionization
• Fundamental Physics with the Square Kilometre Array
• Pre-reionization Fossils, Ultra-faint Dwarfs and the Missing Galactic Satellite Problem
• Where are the Fossils of the First Galaxies? II. True Fossils, Ghost Halos, and the Missing Bright Satellites
• The 21 Centimeter Background from the Cosmic Dark Ages: Minihalos and the Intergalactic Medium before Reionization
• The Kinetic Sunyaev-Zel'dovich Effect from Patchy Reionization: the View from the Simulations