We use a set of numerical simulations to generate 21 cm emission maps under different assumptions regarding the physical conditions at high redshifts. The main aim of our work is to study how the topology of the neutral regions depend on (i) the precise nature of recombination within high-density regions (which would determine whether reionization evolved as inside-out or outside-in) and (ii) the distribution of photon sources. Our results show that the slope of the power spectrum of 21 cm fluctuations would be able to distinguish between the inside-out and outside-in scenarios. On the other hand, we find that the amplitude of the power spectrum would put constraints on the distribution of the sources. It should be possible to put stringent constraints on these scenarios using first generation of 21 cm experiments.
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