Central mass profiles of the nearby cool-core galaxy clusters Hydra A and A478*

N. Okabe, K. Umetsu, T. Tamura, Y. Fujita, M. Takizawa, K. Matsushita, Y. Fukazawa, T. Futamase, M. Kawaharada, S. Miyazaki, Y. Mochizuki, K. Nakazawa, T. Ohashi, N. Ota, T. Sasaki, K. Sato, S. I. Tam

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12 Citations (Scopus)


We perform a weak-lensing study of the nearby cool-core galaxy clusters, Hydra A (z = 0.0538) and A478 (z = 0.0881), of which the brightest cluster galaxies (BCGs) host the powerful activities of active galactic nuclei (AGNs). For each cluster, the observed tangential shear profile is described well by either a single Navarro-Frenk-White model or a two-component model including the BCG as an unresolved point mass. For A478, we determine the BCG and its host-halo masses from a joint fit to weak-lensing and stellar photometry measurements. We find that the choice of initial mass functions (IMFs) can introduce a factor of 2 uncertainty in the BCG mass, whereas the BCG host-halo mass is constrained well by data. We perform a joint analysis of the weak-lensing and stellar kinematics data available for the Hydra A cluster, which allows us to constrain the central mass profile without assuming specific IMFs. We find that the central mass profile (r < 300 kpc) determined from the joint analysis is in excellent agreement with those from independent measurements, including dynamical masses estimated from the cold gas disc component, X-ray hydrostatic total mass estimates, and the central stellar mass estimated with the Salpeter IMF. The observed dark matter fraction around the BCG for Hydra A is found to be smaller than those predicted by adiabatic contraction models, suggesting the importance of other physical processes, such as AGN feedback and/or dissipationless mergers.

Original languageEnglish
Pages (from-to)4475-4487
Number of pages13
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
Publication statusPublished - 2016 Jan 9


  • Galaxies: Clusters: Individual: (Hydra A, A478)
  • Gravitational lensing: Weak

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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