Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The ESO Nearby Abell Cluster Survey IX. The morphology-radius and
  morphology-density relations in rich galaxy clusters   We study the morphology-radius (MR-) and morphology-density (MD-) relations
for a sample of about 850 galaxies (with M <= -19.5) in 23 clusters from the
ENACS (ESO Nearby Abell Cluster Survey). On the basis of their radial
distributions we must distinguish: 1. brightest ellipticals (with M < -22), 2.
late spirals, and 3. the ensemble of less bright ellipticals, S0 galaxies and
early spirals. The latter have indistinguishable distributions of projected
radial distance R. The brightest ellipticals are most centrally concentrated,
the late spirals are almost absent from the central regions and the other
classes are intermediate. Radial segregation of the ellipticals is due to the
brightest ellipticals only, that of the spirals to the late spirals only. We
derive the MD-relation with two measures of projected density: one using the 10
nearest neighbours (Sigma10) and another using only the nearest neighbour
(Sigma1). The Sigma10 MD-relation only shows a significant difference between
early- and late-type galaxies, but the different galaxy types within those
classes are indistinguishable. However, The Sigma1 MD-relation shows that the
normal 'ellipticals' (with M >= -22), the S0 galaxies and the early spirals
have different Sigma1-distributions. The reason for this is that Sigma1 is much
less correlated with R than is Sigma10, and thus has much less cross-talk from
the (MR-) relation. On average, the 'normal' ellipticals populate environments
with higher projected density than do the S0 galaxies while the early spirals
populate even less dense environments. The segregation of the brightest
ellipticals and the late spirals is driven mostly by global factors, while the
segregation between 'normal' ellipticals, S0 galaxies and early spirals is
driven primarily by local factors.

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The categories of this paper are: math
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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: q-fin
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The categories of this paper are: q-alg
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The categories of this paper are: econ
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The categories of this paper are: hep-ex
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The categories of this paper are: ao-sci
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The categories of this paper are: adap-org
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The categories of this paper are: alg-geom
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The categories of this paper are: chem-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-lat
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The categories of this paper are: hep-ph