How much do turbulence, bulk motions, shocks, and other non-thermal components violate hydrostatic support and bias cluster masses?

Scope

In scope

Cluster-ICM non-thermal pressure fraction, merger-driven dynamics, hydrostatic mass bias, and comparison with lensing/dynamical masses.

Out of scope

Excludes results centered on galaxy-CGM depletion or early-type-galaxy L_X--T evolution, and cluster-member statistics without an ICM hot-gas constraint.

Why it matters

Explicitly connects ICM thermodynamic structure to pressure support, gas inventories, and systematics in cluster mass inference.

Competing explanations

• Turbulence, bulk motions, and merger shocks dominate non-thermal support, making HSE bias strongly dynamical-state- and radius-dependent
• Cosmic-ray or magnetic pressure contributes comparably to gas motions
• Residual motions are small in relaxed massive clusters, leaving HSE masses biased by less than about 10%

Discriminating observables

• XRISM/Athena line widths and bulk velocities
• HSE-to-lensing/dynamical mass ratio
• Entropy/pressure maps and shock diagnostics in disturbed clusters
• Comparison of tSZ and X-ray pressure profiles

Blockers

• Background, calibration, and projection
• Multitemperature ICM and hydrostatic assumptions
• Merger stage, geometry, and mass calibration