Nonhydrostatic Gas in the Core of the Relaxed Galaxy Cluster A1795

By M. Markevitch, Alexey Vikhlinin, A. Vikhlinin, P. Mazzotta. 2001

183 citations recorded by the source corpus.

Chandra data on A1795 reveal a mild edge-shaped discontinuity in the gas density 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 outside, while the pressure is continuous, indicating that this is a "cold front," the surface of contact between two moving gases. The continuity of the pressure indicates that the current relative velocity of the gases is near zero, making the edge appear to be in hydrostatic equilibrium. However, a total mass profile, derived from the data in this sector under the equilibrium assumption, exhibits an unphysical jump by a factor of 2, with the mass inside 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 maximum displacement, where it has zero velocity but nonzero centripetal acceleration. The distribution of this nonhydrostatic gas should reflect the reduced gravity force in the accelerating reference frame, resulting in the apparent mass discontinuity. Assuming that the gas outside the edge is hydrostatic, the acceleration of the moving gas can be estimated from the mass jump, a ~ 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 current thermal energy. The length of the cool filament extending from the cD 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 central gravitational potential by past subcluster infall.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/4f84017a0e4b61fedc482a6ab669f6f320fdbd07

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What is a cool-core cluster? a detailed analysis of the cores of the X-ray flux-limited HIFLUGCS cluster sample (2009, background): “Early core studies with Chandrawere done by Fabian et al. (2001) and Markevitch et al. (2001).”
Deep inside the core of Abell 1795: the Chandra view (2001, background): “The presence of breaks in the brightness distribution is now routinely observed inChandradata of galaxy clusters (e.g. Allen, Ettori, Fabian 2001, Markevitch et al. 2001, Vikhlinin et al. 2001, Mazzotta et al. 2001) and is mainly associated with discontinuities in the gas density profile probably…”
STIRRING UP THE POT: CAN COOLING FLOWS IN GALAXY CLUSTERS BE QUENCHED BY GAS SLOSHING? (2009, background): “…arc-like gas density discontinuities (“cold fronts”), concentric with respect to the brightness peak of the cluster (e.g., Mazzotta et al. 2001; Markevitch et al. 2001, 2003b; Churazov et al. 2003; Ascasibar & Markevitch 2006, hereafter AM06; for a review of observations and simulations…”
Comparing the temperatures of galaxy clusters from hydrodynamical N-body simulations to Chandra and XMM-Newton observations (2004, background): “…Vikhlinin, Markevitch & Murray 2001; Mazzotta, Edge & Markevitch 2003), cavities (Fabian et al. 2000; McNamara et al. 2000; Blanton et al. 2001; Markevitch et al. 2001; McNamara et al. 2001; Heinz et al. 2002; Johnstone et al. 2002; Mazzotta et al. 2002; Sanders & Fabian 2002; Smith et al.…”
XMM-Newton Observations of the Perseus Cluster. I. The Temperature and Surface Brightness Structure (2003, background): “Markevitch et al. (2001, 2002) suggested that dissipation of the sloshing kinetic energy may be sufficient to offset radiative gas cooling.”
The impact of mergers on relaxed X-ray clusters – I. Dynamical evolution and emergent transient structures (2006, background): “Explored mechanisms capable of driving such motions include the activity of jets from central AGN (Fabian et al. 2005) or gravitationally induced motions due to small passing substructure (Markevitch et al. 2001; Tittley & Henriksen 2005).”
On the Origin of Radio Halos in Galaxy Clusters (2001, background): “…X-ray temperature distribution where relatively cool gas exists within the central few hundred kpc and hotter gas, consistent with shock-heating, is located at larger radii (e.g., Henry & Briel 1995; Henriksen & Markevitch 1996; Markevitch et al. 1999,2001; Henriksen et al. 2000; Sarazin 2000).”
High-Resolution X-Ray Spectroscopic Constraints on Cooling-Flow Models for Clusters of Galaxies (2002, background): “—Markevitch et al. (2001) has shown that clusters previously thought to be fully relaxed exhibit temperature fronts consistent with plasma exhibiting large bulk motions in the gravitational potential.”
The dark matter haloes of massive, relaxed galaxy clusters observed with Chandra (2006, background): “…of residual substructure in the innermost regions, which probably result from ‘sloshing’ of the X-ray emitting gas within the central potentials (e.g., Markevitch et al. 2001; Ascasibar & Markevitch 2006; Allen et al. 1992) and/or interactions between central radio sources and the surrounding…”
Determination of the Cosmic Distance Scale from Sunyaev-Zel’dovich Effect and Chandra X-Ray Measurements of High-Redshift Galaxy Clusters (2005, background): “In addition, even clusters with X-ray – 20 – structures in the core are normally in pressure equilibrium (Markevitch et al. 2000, 2001), and should therefore have smooth SZE profiles.”