Spiraling into the `snail' cluster MCXC J0157.4-0550

Abstract

We present a deep Chandra (130 ks) study of a striking, tidally induced cold front in a subcluster merging with the galaxy cluster MCXC J0157.4-0550. The subcluster, nicknamed the `snail' (J0157), displays an extensive spiral structure that extends to $\sim 260$ kpc --- one of the largest spiral cold fronts identified to date. Surface brightness and spectral analysis across four sectors reveal a consistent density jump of a factor of $\sim 3$ across the front, together with significant temperature discontinuities, and thermodynamic mapping further delineates the coherent, low-entropy structure of the stripped gas. Unlike classical sloshing cold fronts, the spiral in J0157 arises not from oscillation of a displaced cool core, but from subcluster gas that has been ram pressure stripped and tidally wound into a spiral by orbital rotation. Applying Gaussian Gradient Magnitude filtering and azimuthal surface-brightness analysis, we identify quasi-periodic corrugations along the front consistent with candidate Kelvin-Helmholtz (KH) instabilities, with a characteristic scale of $\sim 90$ kpc. The presence of these KH rolls constrains the effective ICM viscosity to $\lesssim 0.59$ times the Spitzer value and the magnetic field strength at the interface to $\lesssim 5.9\ μ$G. These results establish J0157 as a useful laboratory for probing macro-scale merger-induced gas dynamics and micro-scale plasma transport processes in the intracluster medium.