Browsing by Author "Mao, Yi"

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    Cosmology on the largest scales with the SKA
    (Proceedings of Science, 2014) Camera, Stefano; Raccanelli, Alvise; Bull, Philip; Bertacca, Daniele; Chen, Xuelei; Ferreira, Pedro G.; Kunz, Martin; Maartens, Roy; Mao, Yi; Santos, Mario G.; Shapiro, Paul R.; Viel, Matteo; Xug, Yidong
    The study of the Universe on ultra-large scales is one of the major science cases for the Square Kilometre Array (SKA). The SKA will be able to probe a vast volume of the cosmos, thus representing a unique instrument, amongst next-generation cosmological experiments, for scrutinising the Universe’s properties on the largest cosmic scales. Probing cosmic structures on extremely large scales will have many advantages. For instance, the growth of perturbations is well understood for those modes, since it falls fully within the linear régime. Also, such scales are unaffected by the poorly understood feedback of baryonic physics. On ultra-large cosmic scales, two key effects become significant: primordial non-Gaussianity and relativistic corrections to cosmological observables. Moreover, if late-time acceleration is driven not by dark energy but by modifications to general relativity, then such modifications should become apparent near and above the horizon scale. As a result, the SKA is forecast to deliver transformational constraints on non-Gaussianity and to probe gravity on super-horizon scales for the first time.
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    Probing reionization with LOFAR (Low Frequency Array) using 21-cm redshift space distortions
    (Oxford University Press, 2013) Jensen, Hannes; Datta, Kanan K.; Santos, Mario G.; Mellema, Garrelt; Chapman, Emma; Abdalla, Filipe B.; Iliev, Ilian T.; Mao, Yi; Shapiro, Paul R.; Zaroubi, Saleem; Bernardi, Gianni; Brentjens, M. A.; de Bruyn, A. G.; Ciardi, B.; Harker, G. J. A.; Jelić, V.; Kazemi, S.; Koopmans, L. V. E.; Labropoulos, P.; Martinez, O.; Offringa, A. R.; Pandey, V. N.; Schaye, J.; Thomas, R. M.; Veligatla, V.; Vedantham, H.; Yatawatta, S.
    One of the most promising ways to study the epoch of reionization (EoR) is through radio observations of the redshifted 21-cm line emission from neutral hydrogen. These observations are complicated by the fact that the mapping of redshifts to line-of-sight positions is distorted by the peculiar velocities of the gas. Such distortions can be a source of error if they are not properly understood, but they also encode information about cosmology and astrophysics. We study the effects of redshift space distortions on the power spectrum of 21-cm radiation from the EoR using large-scale N-body and radiative transfer simulations. We quantify the anisotropy introduced in the 21-cm power spectrum by redshift space distortions and show how it evolves as reionization progresses and how it relates to the underlying physics. We go on to study the effects of redshift space distortions on LOFAR observations, taking instrument noise and foreground subtraction into account.We find that LOFAR should be able to directly observe the power spectrum anisotropy due to redshift space distortions at spatial scales around k ∼ 0.1Mpc−1 after 1000 h of integration time. At larger scales, sample errors become a limiting factor, while at smaller scales detector noise and foregrounds make the extraction of the signal problematic. Finally, we show how the astrophysical information contained in the evolution of the anisotropy of the 21-cm power spectrum can be extracted from LOFAR observations, and how it can be used to distinguish between different reionization scenarios.