The Dissection of Abell 2744: A Rich Cluster Growing Through Major and
  Minor Mergers
  New Chandra X-ray data and extensive optical spectroscopy, obtained with
AAOmega on the 3.9 m Anglo-Australian Telescope, are used to study the complex
merger taking place in the galaxy cluster Abell 2744. Combining our spectra
with data from the literature provides a catalog of 1237 redshifts for
extragalactic objects lying within 15' of the cluster center. From these, we
confirm 343 cluster members projected within 3 Mpc of the cluster center.
Combining positions and velocities, we identify two major substructures,
corresponding to the remnants of two major subclusters. The new data are
consistent with a post core passage, major merger taking place along an axis
that is tilted well out of the plane of the sky, together with an interloping
minor merger. Supporting this interpretation, the new X-ray data reveal
enriched, low entropy gas from the core of the approaching, major subcluster,
lying ~2' north of the cluster center, and a shock front to the southeast of
the previously known bright, compact core associated with the receding
subcluster. The X-ray morphology of the compact core is consistent with a
Bullet-like cluster viewed from within ~45 degrees of the merger axis. An X-ray
peak ~3' northwest of the cluster center, with an associated cold front to the
northeast and a trail of low entropy gas to the south, is interpreted as the
remnant of an interloping minor merger taking place roughly in the plane of the
sky. We infer approximate paths for the three merging components.
