We explore the possibility that extended disks , such as that recently discovered in M31 , are the result of a single dwarf ( 10 ^ { 9 } – 10 ^ { 10 } M _ { \odot } ) satellite merger .
We conduct N-body simulations of dwarf NFW halos with embedded spheriodal stellar components on co-planar , prograde orbits in a M31-like host galaxy .
As the orbit decays due to dynamical friction and the system is disrupted , the stellar particles relax to form an extended , exponential disk-like structure that spans the radial range 30 – 200 kpc .
The disk scale-length R _ { d } correlates with the initial extent of the stellar component within the satellite halo : the more embedded the stars , the smaller the resulting disk scale-length .
If the progenitors start on circular orbits , the kinematics of the stars that make up the extended disk have an average rotational motion that is 30 - 50 km/s lower than the host ’ s circular velocity .
For dwarf galaxies moving on highly eccentric orbits ( e \simeq 0.7 ) , the stellar debris exhibits a much lower rotational velocity .
Our results imply that extended galactic disks might be a generic feature of the hierarchical formation of spiral galaxies such as M31 and the Milky Way .