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arXiv · 1801.01592

21CMMC with a 3D light-cone: the impact of the co-evolution approximation on the astrophysics of reionisation and cosmic dawn

Bradley Greig·Andrei Mesinger
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Abstract

We extend 21CMMC, a Monte Carlo Markov Chain sampler of 3D reionisation simulations, to perform parameter estimation directly on 3D light-cones of the cosmic 21cm signal. This brings theoretical analysis closer to the tomographic 21-cm observations achievable with next generation interferometers like HERA and the SKA. Parameter recovery can therefore account for modes which evolve with redshift/frequency. Additionally, simulated data can be more easily corrupted to resemble real data. Using the light-cone version of 21CMMC, we quantify the biases in the recovered astrophysical parameters if we use the 21cm power spectrum from the co-evolution approximation to fit a 3D light-cone mock observation. While ignoring the light-cone effect under most assumptions will not significantly bias the recovered astrophysical parameters, it can lead to an underestimation of the associated uncertainty. However significant biases ($\sim$few -- 10 $σ$) can occur if the 21cm signal evolves rapidly (i.e. the epochs of reionisation and heating overlap significantly) and: (i) foreground removal is very efficient, allowing large physical scales ($k\lesssim0.1$~Mpc$^{-1}$) to be used in the analysis or (ii) theoretical modelling is accurate to within $\sim10$ per cent in the power spectrum amplitude.

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Bradley Greig, Andrei Mesinger. 2018-01-05. 21CMMC with a 3D light-cone: the impact of the co-evolution approximation on the astrophysics of reionisation and cosmic dawn. https://doi.org/10.1093/mnras%2Fsty796

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