Intracluster Medium Velocity Mapping with LEM

Velocity field of intracluster medium (ICM) encodes a wealth of information on large-scale structures in the Universe. Its measurement is vital for studying cluster formation and evolution, weakly-magnetized plasma physics, and cluster cosmology. The Line Emission Mapper (LEM) mission will offer a unique opportunity to directly and efficiently map gas kinematics in the cluster outskirts, up to R₂₀₀ and beyond, where mergers and accretion drive shocks and turbulence and contribute significant nonthermal pressure support to the ICM.

Here we demonstrate the capacity of LEM in cluster studies. Thanks to its unrivaled spectral resolution and grasp, LEM will resolve individual emission lines from multiple gas components along the line of sight and measure their corresponding temperatures and velocities, mapping the entire nearby clusters. It will provide unprecedented views of galaxy clusters – their thermodynamics and kinematics. The specific scientific objectives include but are not limited to (1) detecting gas inflows along cosmic filaments and their interaction with the ICM, (2) probing merger-driven shockwaves and gas stripping, and (3) measuring turbulence and nonthermal pressure in the cluster outskirts.