First detection of a virial shock with SZ data: implication for the mass accretion rate of Abell 2319
Centro de Estudios de Física del Cosmos de Aragón (CEFCA), Plaza de San Juan 1, planta 2, 44001 Teruel, Spain
2 Physics department, Ben-Gurion University of the Negev, POB 653, Be’er Sheva 84105, Israel
Accepted: 12 December 2018
Shocks produced by the accretion of infalling gas in the outskirts 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 8.6σ, using Planck thermal Sunyaev-Zel’dovich data. The shock is located at (2.93 ± 0.05) × R500 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, 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 Ṁ ≃ (1.4 ± 0.4) × 1014 M⊙ Gyr−1 for a total mass of M200 ≃ 1015 M⊙.
Key words: cosmic background radiation / galaxies: clusters: intracluster medium / galaxies: clusters: individual: A2319
© ESO 2019