Stripped Elliptical Galaxies as Probes of ICM Physics. III. Deep Chandra Observations of NGC 4552: Measuring the Viscosity of the Intracluster Medium

R. P. Kraft, E. Roediger, M. Machacek, W. R. Forman, P. E.J. Nulsen, C. Jones, E. Churazov, S. Randall, Y. Su, A. Sheardown

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


We present results from a deep (200 ks) Chandra observation of the early-type galaxy NGC 4552 (M89), which is falling into the Virgo cluster. Previous shallower X-ray observations of this galaxy showed a remnant gas core, a tail to the South of the galaxy, and twin "horns" attached to the northern edge of the gas core. In our deeper data, we detect a diffuse, low surface brightness extension to the previously known tail, and measure the temperature structure within the tail. We combine the deep Chandra data with archival XMM-Newton observations to put a strong upper limit on the diffuse emission of the tail out to a large distance (10× the radius of the remnant core) from the galaxy center. In our two previous papers, we presented the results of hydrodynamical simulations of ram pressure stripping specifically for M89 falling into the Virgo cluster and investigated the effect of intracluster medium (ICM) viscosity. In this paper, we compare our deep data with our specifically tailored simulations and conclude that the observed morphology of the stripped tail in NGC 4552 is most similar to the inviscid models. We conclude that, to the extent the transport processes can be simply modeled as a hydrodynamic viscosity, the ICM viscosity is negligible. More generally, any micro-scale description of the transport processes in the high-β plasma of the cluster ICM must be consistent with the efficient mixing observed in the stripped tail on macroscopic scales.

Original languageEnglish
Article number27
JournalAstrophysical Journal
Issue number1
StatePublished - Oct 10 2017

Bibliographical note

Funding Information:
This work was supported by NASA grants NAS8-03060 and NAS-GO2-1314X. E.R. acknowledges support by the Priority Programs 1177 (“Witness of Cosmic History”) and 1573 (“Physics of the Interstellar Medium”) of the DFG (German Research Foundation), the supercomputing grants NIC 4368 and 5027 at the Jülich Supercomputing Center, a visiting scientist fellowship at the Smithsonian Astrophysical Observatory, and the hospitality of the Harvard/Smithsonian Center for Astrophysics in Cambridge, MA. We would like to thank the anonymous referee for many recommendations that significantly strengthened this paper.

Publisher Copyright:
© 2017. The American Astronomical Society. All rights reserved.


  • X-rays: galaxies
  • X-rays: galaxies: clusters
  • galaxies: clusters: intracluster medium

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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