Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Planes of satellite galaxies: when exceptions are the rule   The detection of planar structures within the satellite systems of both the
Milky Way (MW) and Andromeda (M31) has been reported as being in stark
contradiction to the predictions of the standard cosmological model
($\Lambda$CDM). Given the ambiguity in defining a planar configuration, it is
unclear how to interpret the low incidence of the MW and M31 planes in
$\Lambda$CDM. We investigate the prevalence of satellite planes around galactic
mass haloes identified in high resolution cosmological simulations. We find
that planar structures are very common, and that ~10% of $\Lambda$CDM haloes
have even more prominent planes than those present in the Local Group. While
ubiquitous, the planes of satellite galaxies show a large diversity in their
properties. This precludes using one or two systems as small scale probes of
cosmology, since a large sample of satellite systems is needed to obtain a good
measure of the object-to-object variation. This very diversity has been
misinterpreted as a discrepancy between the satellite planes observed in the
Local Group and $\Lambda$CDM predictions. In fact, ~10% of $\Lambda$CDM
galactic haloes have planes of satellites that are as infrequent as the MW and
M31 planes. The look-elsewhere effect plays an important role in assessing the
detection significance of satellite planes and accounting for it leads to
overestimating the significance level by a factor of 30 and 100 for the MW and
M31 systems, respectively.

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The categories of this paper are: q-alg
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The categories of this paper are: solv-int
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The categories of this paper are: patt-sol
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The categories of this paper are: funct-an
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The categories of this paper are: econ
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The categories of this paper are: atom-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: hep-th
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The categories of this paper are: stat
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The categories of this paper are: cmp-lg
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The categories of this paper are: supr-con
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The categories of this paper are: dg-ga
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The categories of this paper are: acc-phys
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The categories of this paper are: cond-mat
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The categories of this paper are: hep-ph
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The categories of this paper are: chem-ph