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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 (few -- 10) 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 (k0. 1~Mpc^-1) to be used in the analysis or (ii) theoretical modelling is accurate to within 10 per cent in the power spectrum amplitude.
Greig et al. (Mon,) studied this question.