IRREGULAR SLOSHING COLD FRONTS IN THE NEARBY MERGING GROUPS NGC 7618 AND UGC 12491: EVIDENCE FOR KELVIN-HELMHOLTZ INSTABILITIES

Journal Article · Wed Aug 01 04:00:00 EDT 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/754/2/147· OSTI ID:22039209

Roediger, E ^[1]; Kraft, R P; Machacek, M E; Forman, W R; Nulsen, P E. J.; Jones, C

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1. School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, 28759 Bremen (Germany)

We present results from two {approx}30 ks Chandra observations of the hot atmospheres of the merging galaxy groups centered around NGC 7618 and UGC 12491. Our images show the presence of arc-like sloshing cold fronts (CFs) wrapped around each group center and {approx}100 kpc long spiral tails in both groups. Most interestingly, the CFs are highly distorted in both groups, exhibiting 'wings' along the fronts. These features resemble the structures predicted from non-viscous hydrodynamic simulations of gas sloshing, where Kelvin-Helmholtz instabilities (KHIs) distort the CFs. This is in contrast to the structure seen in many other sloshing and merger CFs, which are smooth and featureless at the current observational resolution. Both magnetic fields and viscosity have been invoked to explain the absence of KHIs in these smooth CFs, but the NGC 7618/UGC 12491 pair are two in a growing number of both sloshing and merger CFs that appear distorted. Magnetic fields and/or viscosity may be able to suppress the growth of KHIs at the CFs in some clusters and groups, but clearly not in all. We propose that the presence or absence of KHI distortions in CFs can be used as a measure of the effective viscosity and/or magnetic field strengths in the intracluster medium.

• OSTI ID: 22039209
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 754; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ASTROPHYSICS
COMPUTERIZED SIMULATION
GALAXY CLUSTERS
GAMMA ASTRONOMY
HELMHOLTZ INSTABILITY
HYDRODYNAMICS
IMAGES
MAGNETIC FIELDS
RESOLUTION
STELLAR ATMOSPHERES
VISCOSITY
X-RAY GALAXIES