Inferring the astrophysics of reionization and cosmic dawn from galaxy luminosity functions and the 21-cm signal

The properties of the first galaxies, expected to drive the Cosmic Dawn and the Epoch of Reionization, are encoded in the 3D structure of the cosmic 21-cm signal. Parameter inference from upcoming 21-cm observations promises to revolutionize our understanding of these unseen galaxies. However, prior inference was done using models with several simplifying assumptions. Here we introduce a flexible, physically motivated parametrization for highz galaxy properties, implementing it in the public code 21CMFAST. In particular, we allow their star formation rates and ionizing escape fraction to scale with the masses of their host dark matter haloes, and directly compute inhomogeneous, sub-grid recombinations in the intergalactic medium.Combining current Hubble observations of the rest-frameUVluminosity function (UV LF) at high-z with a mock 1000-h 21-cm observation using the Hydrogen Epoch of Reionization Arrays, we constrain the parameters of our model using aMonte Carlo Markov Chain sampler of 3D simulations, 21CMMC. We show that the amplitude and scaling of the stellar mass with halo mass are strongly constrained by LF observations, while the remaining galaxy properties are constrained mainly by 21-cm observations. The two data sets compliment each other quite well, mitigating degeneracies intrinsic to each observation. All eight of our astrophysical parameters are able to be constrained at the level of ∼10 per cent or better. The updated versions of 21CMFAST and 21CMMC used in this work are publicly available.