Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Galactic Metallicity Gradients Derived from a Sample of OB Stars   The distribution of stellar abundances along the Galactic disk is an
important constraint for models of chemical evolution and Galaxy formation. In
this study we derive radial gradients of C, N, O, Mg, Al, Si, as well as S,
from abundance determinations in young OB stars. Our database is composed of a
sample of 69 members of 25 open clusters, OB associations and H II regions with
Galactocentric distances between 4.7 and 13.2 kpc. An important feature of this
abundance database is the fact that the abundances were derived
self-consistently in non-LTE using a homogeneous set of stellar parameters.
Such an uniform analysis is expected to reduce the magnitude of random errors,
as well as the influence of systematics in the gradients defined by the
abundance and Galactocentric distance. The metallicity gradients obtained in
this study are, in general, flatter than the results from previous recent
abundance studies of early-type stars. The slopes are found to be between
-0.031 (for oxygen) and $-0.052 dex kpc^{-1}$ (for magnesium). The gradients
obtained for the studied elements are quite similar and if averaged, they can
be represented by a single slope of $-0.042 \pm 0.007 dex kpc^{-1}$. This value
is generally consistent with an overall flattening of the radial gradients with
time.

4
The categories of this paper are: cond-mat
19
The categories of this paper are: eess
5
The categories of this paper are: gr-qc
8
The categories of this paper are: hep-ex
24
The categories of this paper are: dg-ga
21
The categories of this paper are: adap-org
10
The categories of this paper are: q-bio
35
The categories of this paper are: mtrl-th
1
The categories of this paper are: cs
36
The categories of this paper are: cmp-lg
0
The categories of this paper are: hep-ph
7
The categories of this paper are: hep-th
3
The categories of this paper are: physics
12
The categories of this paper are: nucl-th
23
The categories of this paper are: solv-int
34
The categories of this paper are: chem-ph