A Moving Cold Front in the Intergalactic Medium of A3667

By A. Vikhlinin, M. Markevitch, S. S. Murray. 2000

322 citations recorded by the source corpus.

We present results from a Chandra observation of the central region of the galaxy cluster A3667 with emphasis on the prominent sharp X-ray brightness edge spanning 0.5 Mpc near the cluster core. Our temperature map shows large-scale nonuniformities characteristic of the ongoing merger, in agreement with earlier ASCA results. The brightness edge turns out to be a boundary of a large cool gas cloud moving through the hot ambient gas, very similar to the "cold fronts" discovered by Chandra in A2142. The higher quality of the A3667 data allows the direct determination of the cloud velocity. At the leading edge of the cloud, the gas density abruptly increases by a factor of 3.9 ± 0.8, while the temperature decreases by a factor of 1.9 ± 0.2 (from 7.7 to 4.1 keV). The ratio of the gas pressures inside and outside the front shows that the cloud moves through the ambient gas at near-sonic velocity, M = 1 ± 0.2 or v = 1400 ± 300 km s-1. In front of the cloud, we observe the compression of the ambient gas with an amplitude expected for such a velocity. A smaller surface brightness discontinuity is observed further ahead, ~350 kpc in front of the cloud. We suggest that it corresponds to a weak bow shock, implying that the cloud velocity may be slightly supersonic. Given all the evidence, the cold front appears to delineate the remnant of a cool subcluster that recently has merged with A3667. The cold front is remarkably sharp. The upper limit on its width, 3.″5 or 5 kpc, is several times smaller than the Coulomb mean free path. This is a direct observation of suppression of the transport processes in the intergalactic medium, most likely by magnetic fields.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/a1be44e43e360b28f9ac48d4968bc1c5753ba76b

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Citations in the corpus

The speed of the ‘bullet’ in the merging galaxy cluster 1E0657−56 (2007, background): “We also disregard magnetic fields, which could in principle play an important role in stabilizing cold front against fluid instabilities and thermal conduction (Ettori & Fabian 2000; Vikhlinin et al. 2001b; Lyutikov 2006).”
What is a cool-core cluster? a detailed analysis of the cores of the X-ray flux-limited HIFLUGCS cluster sample (2009, background): “A3667 This well-known merging cluster shows a very sharp cold front (Vikhlinin et al. 2001b,a) and two radio relics (e.g Roettiger et al. 1999).”
Discovery of a Ringlike Dark Matter Structure in the Core of the Galaxy Cluster Cl 0024+17 (2007, background): “Recently, there have been a number of reports on the detection of such clusters especially from X-rays (e.g., Mazzotta et al. 2001; Vikhlinin et al. 2001; Markevitch et al. 2002; Dupke & White 2003; Henry et al. 2004; Belsole et al. 2005; Ferrari et al. 2006).”
Deep inside the core of Abell 1795: the Chandra view (2001, background): “…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 due either to the…”
Thermal Conduction in Clusters of Galaxies (2001, background): “Chandra has found evidence for sharp temperature jumps in a few clusters, e.g., Abell 2142 (Markevitch et al. 2000) and Abell 3667 (Vikhlinin et al. 2001).”
Shocks and cold fronts in galaxy clusters (2007, background): “Cold fronts — diffusion and conduction barriers A3667 • Width of density jump d < 4 kpc < λe (Coulomb) ≈ 10–15 kpc → diffusion across front is suppressed (magnetic barriers) Vikhlinin et al. 01, M & V 07”
Draping of Cluster Magnetic Fields over Bullets and Bubbles—Morphology and Dynamic Effects (2007, unknown): “We derive an expression for the maximum magnetic field strength and thickness of the layer, as well as for the opening angle of the magnetic wake.”
Nonhydrostatic Gas in the Core of the Relaxed Galaxy Cluster A1795 (2001, background): “This leaves little or no room for a relative gas motion since the ram pressure from such a motion would cause the inner thermal pressure to be higher compared with that on the outside (beyond the small stagnation region), as is indeed seen in A3667 (Vikhlinin et al. 2001).”
Models of Galaxy Clusters with Thermal Conduction (2002, background): “Vikhlinin et al. (2001b) have argued that the magnetic field is stretched out parallel to the cold front by the motion of the infalling galaxy/group and that this explains the very low conductivity.”