Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The outer rotation curve of the Milky Way   A straightforward determination of the circular-speed curve vc(R) of the
Milky Way suggests that near the Sun, vc starts to rise approximately linearly
with R. If this result were correct, the Galactic mass density would have to be
independent of radius at R ~> R0. We show that the apparent linear rise in v_c
arises naturally if the true circular-speed curve is about constant or gently
falling at R0 < R ~< 2 R0, but most tracers that appear to be at R ~> 1.25 R0
are actually concentrated into a ring of radius ~1.6 R0.

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The categories of this paper are: hep-ph
23
The categories of this paper are: solv-int
1
The categories of this paper are: cs
9
The categories of this paper are: nlin
10
The categories of this paper are: q-bio
22
The categories of this paper are: chao-dyn
20
The categories of this paper are: acc-phys
35
The categories of this paper are: mtrl-th
37
The categories of this paper are: supr-con
28
The categories of this paper are: alg-geom
32
The categories of this paper are: atom-ph
7
The categories of this paper are: hep-th
14
The categories of this paper are: math-ph
11
The categories of this paper are: hep-lat
36
The categories of this paper are: cmp-lg
2
The categories of this paper are: math