Architecture of the Andromeda: a quantitative analysis of clustering in the inner stellar halo
arXiv:1610.05920 · doi:10.1093/mnras/stw2732
Abstract
We present a quantitative measurement of the amount of clustering present in the inner 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 at maximum and on average . Importantly, comparing against the 11 stellar halo models of \cite{2005ApJ...635..931B}, which were simulated within the context of the cosmological paradigm, we find that the amount of substructures in the M31 stellar halo closely resembles that of a typical halo.
arXiv comment9 pages, to appear in MNRAS
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