ABELL 1201: The anatomy of a cold front cluster from combined optical and x-ray data

Matt S. Owers*, Paul E J Nulsen, Warrick J. Couch, Maxim Markevitch, Gregory B. Poole

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)


We present a combined X-ray and optical analysis of the cold front cluster Abell 1201 using archival Chandra data and multi-object spectroscopy taken with the 3.9 m Anglo-Australian and 6.5 m Multiple Mirror Telescopes. This paper represents the first in a series presenting a study of a sample of cold front clusters selected from the Chandra archives with the aim of relating cold fronts to merger activity, understanding the dynamics of mergers and their effect on the cluster constituents. The Chandra X-ray imagery of Abell 1201 reveals two conspicuous surface brightness discontinuities that are shown to be cold fronts, and a remnant core structure. Temperature maps reveal a complex multiphase temperature structure with regions of hot gas interspersed with fingers of cold gas. Our optical analysis is based on a sample of 321 confirmed members, whose mean redshift is z = 0.1673 ± 0.0002 and velocity dispersion is 778 ± 36 km s-1. We search for dynamical substructure and find clear evidence for multiple localized velocity substructures coincident with overdensities in the galaxy surface density. Most notably, we find the structure coincident with the remnant X-ray core. Despite the clear evidence for dynamical activity, we find the peculiar velocity distribution does not deviate significantly from Gaussian. We apply two-body dynamical analyses in order to assess which of the substructures are bound, and thus dynamically important in terms of the cluster merger history. We propose that the cold fronts in Abell 1201 are a consequence of its merger with a smaller subunit, which has induced gas motions that gave rise to "sloshing" cold fronts. Abell 1201 illustrates the value of combining multiwavelength data and multiple substructure detection techniques when attempting to ascertain the dynamical state of a cluster.

Original languageEnglish
Pages (from-to)702-722
Number of pages21
JournalAstrophysical Journal
Issue number1
Publication statusPublished - 10 Feb 2009
Externally publishedYes


  • galaxies: clusters: individual (Abell 1201)
  • X-rays: galaxies: clusters


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