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

TL;DR

This paper reports the first detection of a virial shock in galaxy cluster A2319 using SZ data, providing insights into the cluster's accretion processes and mass growth.

Contribution

It presents the first observational detection of a virial shock in A2319 via SZ data, linking shock properties to accretion rates and simulation predictions.

Findings

Shock detected at 2.93 R500 with 8.6σ significance.

Lower limit on Mach number of infalling gas is >3.25.

Estimated accretion rate of A2319 is approximately 1.4 x 10^14 M_sun per Gyr.

Abstract

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. These results are consistent with expectations derived from hydrodynamical simulations. Finally, we use the shock location to constrain the accretion rate of A2319 to $\dot{M} \simeq (1.4 \pm 0.4) \times 10^{14}$ M$_\odot$ Gyr$^{-1}$, for a total mass, $M_{200} \simeq 10^{15}$ M$_\odot$.