The formation of shell galaxies similar to NGC 7600 in the cold dark   matter cosmogony
  We present new deep observations of 'shell' structures in the halo of the nearby elliptical galaxy NGC 7600, alongside a movie of galaxy formation in a cold dark matter universe (available at http://www.virgo.dur.ac.uk/shell-galaxies). The movie, based on an ab initio cosmological simulation, shows how continuous accretion of clumps of dark matter and stars creates a swath of diffuse circumgalactic structures. The disruption of a massive clump on a near-radial orbit creates a complex system of transient concentric shells which bare a striking resemblance to those of NGC 7600. With the aid of the simulation we interpret NGC 7600 in the context of the CDM model. 
Andrew P. Cooper, David Martinez-Delgado, John Helly, Carlos Frenk,   Shaun Cole, Ken Crawford, Stefano Zibetti, Julio A. Ca...
astro-ph.GA astro-ph.CO