The radial alignment of dark matter subhalos: from simulations to observations

Abstract

We explore the radial alignment of subhalos in 2-dimensional projections of cosmological simulations. While most other recent studies focussed on quantifying the signal utilizing the full 3-dimensional spatial information any comparison to observational data has to be done in projection along random lines-of-sight. We have a suite of well resolved host dark matter halos at our disposal ranging from 6 x 10^14 Msun/h down to 6 x 10^13Msun/h. For these host systems we do observe that the major axis of the projected 2D mass distribution of subhalos aligns with its (projected) distance vector to the host's centre. The signal is actually stronger than the observed alignment. However, when considering only the innermost 10-20% of the subhalo's particles for the 2D shape measurement we recover the observed correlation. We further acknowledge that this signal is independent of subhalo mass.

arXiv comment5 pages, 4 figures, accepted for publication as MNRAS Letter

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