Journal
ASTROPHYSICAL JOURNAL LETTERS
Volume 719, Issue 1, Pages L74-L78Publisher
IOP PUBLISHING LTD
DOI: 10.1088/2041-8205/719/1/L74
Keywords
galaxies: clusters: general; galaxies: clusters: intracluster medium; hydrodynamics; intergalactic medium; magnetic fields; X-rays: galaxies: clusters
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Funding
- NASA through Einstein Post-doctoral Fellowship [PF8-90059]
- NASA [NAS8-39073]
- Harvard College Observatory
- NSF [AST-0907890]
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Cold fronts (CFs)-density and temperature plasma discontinuities-are ubiquitous in cool cores of galaxy clusters, where they appear as X-ray brightness edges in the intracluster medium, nearly concentric with the cluster center. We analyze the thermodynamic profiles deprojected across core CFs found in the literature. While the pressure appears continuous across these CFs, we find that all of them require significant centripetal acceleration beneath the front. This is naturally explained by a tangential, nearly sonic bulk flow just below the CF, and a tangential shear flow involving a fair fraction of the plasma beneath the front. Such shear should generate near-equipartition magnetic fields on scales less than or similar to 50 pc from the front and could magnetize the entire core. Such fields would explain the apparent stability of cool core CFs and the recently reported CF-radio minihalo association.
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