Architecture of the Andromeda: a quantitative analysis of clustering in
  the inner stellar halo
  We present a quantitative measurement of the amount of clustering present in
the inner $\sim30$ kpc of the stellar halo of the Andromeda galaxy (M31). For
this we analyse the angular positions and radial velocities of the carefully
selected Planetary Nebulae (PNe) in the M31 stellar halo. We study the
cumulative distribution of pair-wise distances in angular position and line of
sight velocity space, and find that the M31 stellar halo contains substantially
more stars in the form of close pairs as compared to that of a featureless
smooth halo. In comparison to a smoothed/scrambled distribution we estimate
that the clustering excess in the M31 inner halo is roughly $40\%$ at maximum
and on average $\sim 20\%$. Importantly, comparing against the 11 stellar halo
models of \cite{2005ApJ...635..931B}, which were simulated within the context
of the $\Lambda{\rm CDM}$ cosmological paradigm, we find that the amount of
substructures in the M31 stellar halo closely resembles that of a typical
$\Lambda{\rm CDM}$ halo.
