Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Old stellar Galactic disc in near-plane regions according to 2MASS:
  scales, cut-off, flare and warp   We have pursued two different methods to analyze the old stellar population
near the Galactic plane, using data from the 2MASS survey. The first method is
based on the isolation of the red clump giant population in the color-magnitude
diagrams and the inversion of its star counts to obtain directly the density
distribution along the line of sight. The second method fits the parameters of
a disc model to the star counts in 820 regions. Results from both independent
methods are consistent with each other. The qualitative conclusions are that
the disc is well fitted by an exponential distribution in both the
galactocentric distance and height. There is not an abrupt cut-off in the
stellar disc (at least within R<15 kpc). There is a strong flare (i.e. an
increase of scale-height towards the outer Galaxy) which begins well inside the
solar circle, and hence there is a decrease of the scale-height towards the
inner Galaxy. Another notable feature is the existence of a warp in the old
stellar population whose amplitude is coincident with the amplitude of the gas
warp.
  It is shown for low latitude stars (mean height: |z|~300 pc) in the outer
disc (galactocentric radius R>6 kpc) that: the scale-height in the solar circle
is h_z(R_sun)=3.6e-2 R_sun, the scale-length of the surface density is h_R=0.42
R_sun and the scale-length of the space density in the plane (i.e. including
the effect of the flare) is H=0.25 R_sun. The variation of the scale-height due
to the flare follows roughly a law h_z(R) =~ h_z(R_sun) exp
[(R-R_\odot)/([12-0.6R(kpc)] kpc)] (for R<~15 kpc; R_sun=7.9 kpc). The warp
moves the mean position of the disc to a height z_w=1.2e-3 R(kpc)^5.25
sin(phi+(5 deg.)) pc (for R<~13 kpc; R_sun=7.9 kpc).

12
The categories of this paper are: nucl-th
30
The categories of this paper are: q-alg
1
The categories of this paper are: cs
28
The categories of this paper are: alg-geom
31
The categories of this paper are: ao-sci
33
The categories of this paper are: plasm-ph
37
The categories of this paper are: supr-con
15
The categories of this paper are: nucl-ex
17
The categories of this paper are: q-fin
25
The categories of this paper are: patt-sol
4
The categories of this paper are: cond-mat
20
The categories of this paper are: acc-phys
22
The categories of this paper are: chao-dyn
2
The categories of this paper are: math
35
The categories of this paper are: mtrl-th
29
The categories of this paper are: funct-an