First detection of a virial shock with SZ data: implication for the mass accretion rate of Abell 2319

Understand

Shocks produced by the accretion of infalling gas in the outskirt of galaxy clusters are expected in the hierarchical structure formation scenario, as found in cosmological hydrodynamical simulations.

• Here, we report the detection of a shock front at a large radius in the pressure profile of the galaxy cluster A2319 at a significance of $8.6\sigma$, using Planck thermal Sunyaev-Zel'dovich data.
• The shock is located at $(2.93 \pm 0.05) \times R_{500}$ and is not dominated by any preferential radial direction.
• Using a parametric model of the pressure profile, we derive a lower limit on the Mach number of the infalling gas, $\mathcal{M} > 3.25$ at 95\% confidence level.