2008/08/31 by Sunghye Baek, S. Baek, P. Di Matteo +4 · 2 citations
Physics and Astronomy · #Algorithm #Astrophysics #Astrophysics and Cosmic Phenomena #Computation #Computational physics #Computer science #Dark Ages #Galaxies: Formation, Evolution, Phenomena #Galaxy #Mean kinetic temperature #Optics #Physics #Radiative transfer #Radio Astronomy Observations and Technology #Redshift #Reionization #SIGNAL (programming language) #Spectral density #Star formation #Stars #Statistical physics #astro-ph
paper · pdf · doi:10.1051/0004-6361:200810757
20 pages, 16 figures, 2 tables, To be publish A&A. High resolution version available at http://aramis.obspm.fr/~baek/21cm_Lya.pdf
arxiv created 2008/12/01 · openalex publication_date 2008/12/04 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The emission of neutral hydrogen is the most promising probe of the epoch of reionization (EoR). In the next few years, the SKA pathfinders will provide statistical measurements of this signal, such as its power spectrum. Within one decade, SKA should produce a full tomography of the signal. Numerical simulations predicting these observations are necessary to optimize the design of the instruments and help in the interpretation of the data. Simulations are reaching a reasonable level in terms of scale range, but still often rely on simplifications to compute the strength of the signal. The main difficulty is the computation of the spin temperature of neutral hydrogen which depends on the gas kinetic temperature and on the level of the local Lyman-<i>α<i/> flux (The Wouthuysen-Field effect). A assumption is usual. However, this assumption does not apply early in the reionization history, or even later in the history as long as the sources of X-rays are too weak to heat the intergalactic medium significantly. This work presents the first EoR numerical simulations including, beside dynamics and ionizing continuum radiative transfer, a self-consistent treatment of the Ly-<i>α<i/> radiative transfer. This allows us to compute the spin temperature more accurately. We use two different box sizes, and , and a star source model. Using the redshift dependence of average quantities, maps, and power spectra, we quantify the effect of using different assumptions to compute the spin temperature and the influence of the box size. The first effect comes from allowing for a signal in absorption (i.e. not making the approximation). The magnitude of this effect depends on the amount of heating by hydrodynamic shocks and X-rays in the intergalactic medium (IGM). With our source model we have little heating so regions seen in absorption survive almost until the end of reionization. The second effects comes from using the real, local, Lyman-<i>α<i/> flux. This effect is important for an average ionization fraction of less than ~: it changes the overall amplitude of the signal, and adds its own fluctuations to the power spectrum.