Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ca II triplet spectroscopy of RGB stars in NGC 6822: kinematics and
  metallicities   We present a detailed analysis of the chemistry and kinematics of red giants
in the dwarf irregular galaxy NGC 6822. Spectroscopy at 8500 Angstroms was
acquired for 72 red giant stars across two fields using FORS2 at the VLT. Line
of sight extinction was individually estimated for each target star to
accommodate the variable reddening across NGC 6822. The mean radial velocity
was found to be v_helio = (52.8 +/- 2.2) km/s with dispersion rms = 24.1 km/s,
in agreement with other studies. Ca II triplet equivalent widths were converted
into [Fe/H] metallicities using a V magnitude proxy for surface gravity. The
average metallicity was [Fe/H] = (-0.84 +/- 0.04) with dispersion rms = 0.31
dex and interquartile range 0.48. Our assignment of individual reddening values
makes our analysis more sensitive to spatial variations in metallicity than
previous studies. We divide our sample into metal-rich and metal-poor stars;
the former are found to cluster towards small radii with the metal-poor stars
more evenly distributed across the galaxy. The velocity dispersion of the
metal-poor stars is higher than that of the metal-rich stars; combined with the
age-metallicity relation this indicates that older populations have either been
dynamically heated or were born in a less disclike distribution. The low ratio
(v_rot/v_rms) suggests that within the inner 10', NGC 6822's stars are
dynamically decoupled from the HI gas, possibly in a thick disc or spheroid.

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The categories of this paper are: adap-org
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The categories of this paper are: patt-sol
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The categories of this paper are: alg-geom
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The categories of this paper are: atom-ph
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The categories of this paper are: physics
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The categories of this paper are: cmp-lg
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The categories of this paper are: econ
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The categories of this paper are: dg-ga
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The categories of this paper are: q-fin
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The categories of this paper are: quant-ph
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The categories of this paper are: cs
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The categories of this paper are: chao-dyn
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The categories of this paper are: stat
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The categories of this paper are: hep-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: comp-gas