Forward-Modeling the First Billion Years

The birth of the first stars, galaxies and black holes heralded the beginning of the Cosmic Dawn (CD). Their light spread out, ionizing and heating virtually every atom in our Universe culminating in the Epoch of Reionization (EoR). These milestones span the bulk of our cosmic lightcone. Luckily, we are currently experiencing a dramatic increase in observations probing the EoR.

To accommodate this Big Data revolution, we have developed a fully Bayesian framework capable of forward-modeling 3D realizations of the first billion years of our Universe.

Confronting these models with data allows us to constrain the bulk properties of the unseen first galaxies, whose radiation fields drive the CD and EoR, as well as those of the intergalactic medium (IGM).We will jointly sample:

1. flexible scaling relations characterizing the first galaxies
2. cosmological parameters and
3. hyperparameters characterizing systematics.

For each sample, we will compute the 4D evolution of the IGM, and compare the forward-modeled data to available observations.

The resulting (publicly-available) posterior will serve as the current state of knowledge, guiding both observational and theoretical efforts in the coming decade. Because of the enormous dimensionality of parameter space, it is only achievable with PRACE.