Light cone effect on the reionization 21-cm signal - II. Evolution, anisotropies and observational implications
2014 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 442, no 2, 1491-1506 p.Article in journal (Refereed) Published
Measurements of the H i 21-cm power spectra from the reionization epoch will be influenced by the evolution of the signal along the line-of-sight direction of any observed volume. We use numerical as well as seminumerical simulations of reionization in a cubic volume of 607 Mpc across to study this so-called light-cone effect on the H i 21-cm power spectrum. We find that the light-cone effect has the largest impact at two different stages of reionization: one when reionization is similar to 20 per cent and other when it is similar to 80 per cent completed. We find a factor of similar to 4 amplification of the power spectrum at the largest scale available in our simulations. We do not find any significant anisotropy in the 21-cm power spectrum due to the light-cone effect. We argue that for the power spectrum to become anisotropic, the light-cone effect would have to make the ionized bubbles significantly elongated or compressed along the line of sight, which would require extreme reionization scenarios. We also calculate the two-point correlation functions parallel and perpendicular to the line of sight and find them to differ. Finally, we calculate an optimum frequency bandwidth below which the light-cone effect can be neglected when extracting power spectra from observations. We find that if one is willing to accept a 10 per cent error due to the light-cone effect, the optimum frequency bandwidth for k = 0.056 Mpc(-1) is similar to 7.5 MHz. For k = 0.15 and 0.41 Mpc(-1), the optimum bandwidth is similar to 11 and similar to 16 MHz, respectively.
Place, publisher, year, edition, pages
2014. Vol. 442, no 2, 1491-1506 p.
methods: numerical, methods: statistical, cosmology: theory, dark ages, reionization, first stars, diffuse radiation
Astronomy, Astrophysics and Cosmology
Research subject Astronomy
IdentifiersURN: urn:nbn:se:su:diva-107029DOI: 10.1093/mnras/stu927ISI: 000339423100044OAI: oai:DiVA.org:su-107029DiVA: diva2:743601