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Deep Chandra Observation and Numerical Studies of the Nearest Cluster Cold Front in the SkyWe present the results of a very deep (500 ks) Chandra observation, along with tailored numerical simulations, of the nearest, best resolved cluster cold front in the sky, which lies 90 kpc (19 arcmin) to the north-west of M87. The northern part of the front appears the sharpest, with a width smaller than 2.5 kpc (1.5 Coulomb mean free paths; at 99 per cent confidence). Everywhere along the front, the temperature discontinuity is narrower than 4-8 kpc and the metallicity gradient is narrower than 6 kpc, indicating that diffusion, conduction and mixing are suppressed across the interface. Such transport processes can be naturally suppressed by magnetic fields aligned with the cold front. Interestingly, comparison to magnetohydrodynamic simulations indicates that in order to maintain the observed sharp density and temperature discontinuities, conduction must also be suppressed along the magnetic field lines. However, the northwestern part of the cold front is observed to have a non-zero width. While other explanations are possible, the broadening is consistent with the presence of Kelvin-Helmholtz instabilities (KHI) on length-scales of a few kpc. Based on comparison with simulations, the presence of KHI would imply that the effective viscosity of the intracluster medium is suppressed by more than an order of magnitude with respect to the isotropic Spitzer-like temperature dependent viscosity. Underneath the cold front, we observe quasi-linear features that are approximately 10 per cent brighter than the surrounding gas and are separated by approximately 15 kpc from each other in projection. Comparison to tailored numerical simulations suggests that the observed phenomena may be due to the amplification of magnetic fields by gas sloshing in wide layers below the cold front, where the magnetic pressure reaches approximately 5-10 per cent of the thermal pressure, reducing the gas density between the bright features.
Document ID
20170002323
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Werner, N. (Stanford Univ. Stanford, CA, United States)
ZuHone, J. A. (Massachusetts Inst. of Tech. Cambridge, MA, United States)
Zhuravleva, I. (Stanford Univ. Stanford, CA, United States)
Ichinohe, Y. (Institute of Space and Astronautical Science Sagamihara, Japan)
Simionescu, A. (Institute of Space and Astronautical Science Sagamihara, Japan)
Allen, S. W. (Stanford Univ. Stanford, CA, United States)
Markevitch, M. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Fabian, A. C. (Institute of Astronomy Cambridge, United Kingdom)
Keshet, U. (Ben Gurion Univ. of the Negev Beersheva, Israel)
Roediger, E. (Hamburg Univ. Germany)
Ruszkowski, M. (Michigan Univ. Ann Arbor, MI, United States)
Sanders, J. S. (Max-Planck-Inst. fuer Extraterrestrische Physik Garching, Germany)
Date Acquired
March 17, 2017
Publication Date
November 6, 2015
Publication Information
Publication: Monthly Notice of the Royal Astronomical Society
Volume: 455
Issue: 1
ISSN: 0035-8711
Subject Category
Astrophysics
Report/Patent Number
GSFC-E-DAA-TN40090
Funding Number(s)
CONTRACT_GRANT: GO3-14142A
CONTRACT_GRANT: NAS8-03060
CONTRACT_GRANT: SV2-8203
CONTRACT_GRANT: DE-AC02-76SF00515
Distribution Limits
Public
Copyright
Other
Keywords
hydrodynamics
galaxies: clusters: individual: Virgo
X-rays: galaxies: clusters
galaxies: clusters: intracluster medium
instabilities