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Deep Chandra observations of NGC 1404 : cluster plasma physics revealed by an infalling early-type galaxy

Forman, William R.; Kraft, Ralph P.; Randall, Scott W.; Machacek, Marie E.; Roediger, Elke; Churazov, Eugene; Forman, William; Jones, Christine; Kraft, Ralph; Machacek, Marie; Nulsen, Paul; Randall, Scott; Su, Yuanyuan


William R. Forman

Ralph P. Kraft

Scott W. Randall

Marie E. Machacek

Eugene Churazov

William Forman

Christine Jones

Ralph Kraft

Marie Machacek

Paul Nulsen

Scott Randall

Yuanyuan Su


The intracluster medium (ICM), as a magnetized and highly ionized fluid, provides an ideal laboratory to study plasma physics under extreme conditions that cannot yet be achieved on Earth. NGC 1404 is a bright elliptical galaxy that is being gas stripped as it falls through the ICM of the Fornax Cluster. We use the new {\sl Chandra} X-ray observations of NGC 1404 to study ICM microphysics. The interstellar medium (ISM) of NGC 1404 is characterized by a sharp leading edge, 8 kpc from the galaxy center, and a short downstream gaseous tail. Contact discontinuities are resolved on unprecedented spatial scales ($0\farcs5=45$\,pc) due to the combination of the proximity of NGC 1404, the superb spatial resolution of {\sl Chandra}, and the very deep (670 ksec) exposure. At the leading edge, we observe sub-kpc scale eddies generated by Kelvin-Helmholtz instability and put an upper limit of 5\% Spitzer on the isotropic viscosity of the hot cluster plasma. We also observe mixing between the hot cluster gas and the cooler galaxy gas in the downstream stripped tail, which provides further evidence of a low viscosity plasma. The assumed ordered magnetic fields in the ICM ought to be smaller than 5\,μG to allow KHI to develop. The lack of evident magnetic draping layer just outside the contact edge is consistent with such an upper limit.


Kraft, R. P., Forman, W. R., Randall, S. W., Machacek, M. E., Roediger, E., Churazov, E., …Su, Y. (2017). Deep Chandra observations of NGC 1404 : cluster plasma physics revealed by an infalling early-type galaxy. The Astrophysical journal, 834(1), 74.

Acceptance Date Nov 30, 2016
Online Publication Date Jan 4, 2017
Publication Date Jan 4, 2017
Deposit Date Jan 4, 2017
Publicly Available Date Jan 4, 2017
Journal Astrophysical journal
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 834
Issue 1
Article Number 74
Pages 74
Keywords X-rays : galaxies : luminosity; Galaxies : ISM; Galaxies : elliptical and lenticular; Clusters of galaxies : intracluster medium
Public URL
Publisher URL
Additional Information Journal title: The Astrophysical Journal; Article type: paper; Article title: DEEPCHANDRAOBSERVATIONS OF NGC 1404: CLUSTER PLASMA PHYSICS REVEALED BY AN INFALLING EARLY-TYPE GALAXY; Copyright information: © 2017. The American Astronomical Society. All rights reserved.; Date received: 2016-10-13; Date accepted: 2016-11-29; Online publication date: 2017-01-04


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