Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Oxygen and Nitrogen in Isolated Dwarf Irregular Galaxies   We present long slit optical spectroscopy of 67 HII regions in 21 dwarf
irregular galaxies to investigate the enrichment of oxygen, nitrogen, neon,
sulfur, and argon in low mass galaxies. Oxygen abundances are obtained via
direct detection of the temperature sensitive emission lines for 25 HII
regions; for the remainder of the sample, oxygen abundances are estimated from
strong line calibrations. The direct abundance determinations are compared to
the strong-line abundance calibrations of both McGaugh (1991) and Pilyugin
(2000). Global oxygen and nitrogen abundances for this sample of dwarf
irregular galaxies are examined in the context of open and closed box chemical
evolution models. While several galaxies are consistent with closed box
chemical evolution, the majority of this sample have an effective yield ~1/4 of
the expected yield for a constant star formation rate and Salpeter IMF,
indicating that either outflow of enriched gas or inflow of pristine gas has
occurred. The effective yield strongly correlates with M_H/L_B in the sense
that gas-rich galaxies are more likely to be closed systems. However, the
effective yield does not appear to correlate with other global parameters such
as dynamical mass, absolute magnitude, star formation rate or surface
brightness. A correlation is found between the observed nitrogen-to-oxygen
ratio and the color of the underlying stellar population; redder dwarf
irregular galaxies have higher N/O ratios than blue dwarf irregular galaxies.
The relative abundance ratios are interpreted in the context of delayed release
of nitrogen and varied star formation histories.

26
The categories of this paper are: bayes-an
20
The categories of this paper are: acc-phys
18
The categories of this paper are: econ
27
The categories of this paper are: comp-gas
29
The categories of this paper are: funct-an
4
The categories of this paper are: cond-mat
16
The categories of this paper are: stat
24
The categories of this paper are: dg-ga
31
The categories of this paper are: ao-sci
36
The categories of this paper are: cmp-lg
21
The categories of this paper are: adap-org
37
The categories of this paper are: supr-con
1
The categories of this paper are: cs
30
The categories of this paper are: q-alg
7
The categories of this paper are: hep-th
15
The categories of this paper are: nucl-ex