本文章最後由 iheby 於 2015-3-25 23:53 編輯
座談會：「廿一厘米」宇宙學的黃金時代 @中文大學物理系
2015.03.20(五) 16:30 - 17:30
地點：香港中文大學 科學館 L2
講者：茅奕博士 (法國巴黎天體物理研究所 Institut d’Astrophysique de Paris, France)
The neutral hydrogen atoms at high redshift contribute a diffuse background of redshifted 21 cm radiation which encodes information about the physical conditions in the early Universe at z > 6 during and before the Epoch of Reionization. Three-dimensional mapping of cosmic 21 cm background (“21 cm tomography”) has recently emerged as a promising cosmological probe, with arguably greater long-term potential than the cosmic microwave background measurement. I will review the prospect for constraining cosmological parameters, including those beyond the standard ΛCDM model, using 21 cm tomography. To fulfil this promise, further progress is required to ensure that predictions of the cosmic 21cm background are accurate enough. This accuracy depends not only on the realistic astrophysical modelling of reionization and the spin temperature of neutral hydrogen, but also on the accuracy of the methods used to extract the 21 cm signal from simulations of cosmic reionization. While my next seminar talk will focus on the former issue, I will report in this talk the progress on the later. I will present a robust, accurate yet efficient computational scheme to predict the 21cm background in observer redshift space, given real-space simulation data, which accounts for peculiar velocity in the fully nonlinear way. While linear theory allows to separate the cosmological information from the astrophysical information by exploiting the redshift-space distortion of 21 cm power spectrum, nonlinear fluctuations in ionization, density and velocity can change this. Using mock 21 cm data from large-scale reionization simulation, we examine the intrinsic accuracy of the separation scheme for extracting the matter power spectrum from 21cm observations, for the first time.
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