Nonhydrostatic gas in the core of the relaxed galaxy cluster A1795

Chandra data on A1795 reveal a mild edge-shaped discontinuity in the gas de nsity and temperature in the southern sector of the cluster at r = 60 h(-1) kpc. The gas inside the edge is 1.3-1.5 times denser and cooler than outsi de, while the pressure is continuous, indicating that this is a "cold front ," the surface of contact between two moving gases. The continuity of the p ressure indicates that the current relative velocity of the gases is near z ero, making the edge appear to be in hydrostatic equilibrium. However, a to tal mass profile, derived from the data in this sector under the equilibriu m assumption, exhibits an unphysical jump by a factor of 2, with the mass i nside the edge being lower. We propose that the cooler gas is "sloshing" in the cluster gravitational potential well and is now near the point of maxi mum displacement, where it has zero velocity but nonzero centripetal accele ration. The distribution of this nonhydrostatic gas should reflect the redu ced gravity force in the accelerating reference frame, resulting in the app arent mass discontinuity. Assuming that the gas outside the edge is hydrost atic, the acceleration of the moving gas can be estimated from the mass jum p, a similar to 800 h km s(-1) (10(8) yr)(-1). The gravitational potential energy of this gas that is available for dissipation is about half of its c urrent thermal energy. The length of the cool filament extending from the c D galaxy (Fabian et al.) may give the amplitude of the gas sloshing, 30-40 h(-1) kpc. Such gas bulk motion might be caused by a disturbance of the cen tral gravitational potential by past subcluster infall.