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

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


The Fornax Cluster is the nearest (≤20 Mpc) galaxy cluster in the southern sky. NGC?1404 is a bright elliptical galaxy falling through the intracluster medium (ICM) of the Fornax Cluster. The sharp leading edge of NGC 1404 forms a classical "cold front" that separates 0.6 keV dense interstellar medium and 1.5 keV diffuse ICM. We measure the angular pressure variation along the cold front using a very deep (670 ks) Chandra X-ray observation. We are taking the classical approach-using stagnation pressure to determine a substructure's speed-to the next level by not only deriving a general speed but also directionality, which yields the complete velocity field as well as the distance of the substructure directly from the pressure distribution. We find a hydrodynamic model consistent with the pressure jump along NGC 1404 s atmosphere measured in multiple directions. The best-fit model gives an inclination of 33° and a Mach number of 1.3 for the infall of NGC 1404, in agreement with complementary measurements of the motion of NGC 1404. Our study demonstrates the successful treatment of a highly ionized ICM as ideal fluid flow, in support of the hypothesis that magnetic pressure is not dynamically important over most of the virial region of galaxy clusters.

Original languageEnglish
Article number19
JournalAstrophysical Journal
Issue number1
StatePublished - Jan 20 2017

Bibliographical note

Funding Information:
This work was supported by Chandra Awards GO1-12160X and GO2-13125X issued by the Chandra X-ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory under NASA contract NAS8-03060.

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


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

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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