Resolving the Multiscale, Multiphase Universe

Galaxies grow through the reciprocal cycling of gas between disks and their massive surrounding halos.

Despite major strides in observations and simulations, the physics regulating this galactic ecosystem remains unclear, primarily due to the multiphase, multiscale nature of circumgalactic gas.All current cosmological simulations fail to capture the multiphase structure of galactic halos and exhibit a lack of convergence in even the first order gas properties such as the amount of cold gas found.

This strongly limits their applicability in the circumgalactic medium to interpret existing observations as well as their predictive power.ReMMU will breach this barrier by implementing an innovative multi-fluid subgrid model to track unresolved gas phases both in hydrodynamical and radiative transfer simulations.The objectives of ReMMU are to (1) run the first cosmological simulation with converged gas properties and (2) perform a robust comparison with absorption as well as emission line data of galactic ecosystems.This work will shed light on the drivers of galactic growth and feedback mechanisms, the key challenge to understand the formation and evolution of galaxies.Only recent advances in fundamental hydrodynamical theory have constrained the parameter space sufficiently and, thus, opened the pathway for subgrid models of unresolved gas.

Simultaneously, a rapidly growing body of observational surveys started to revolutionize the available data on galactic ecosystems.Hence, ReMMU is particularly timely combining these advances: it will exploit the theoretical progress in a full cosmological context and establish firm predictions for comparison with observations across cosmic time, ultimately breaking the current impasse.

The PI has made significant contributions in the theory of small scale hydrodynamical as well as radiative transfer problems and is, therefore, uniquely suited to establish a world-leading team to carry out ReMMU.