Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Emission Line Abundances of Absorption Selected Galaxies at z<0.5   We have obtained optical spectra of four galaxies associated with MgII QSO
absorbers at redshifts 0.10 < z < 0.45. We calculate the gas-phase oxygen
abundance of these galaxies using the empirical R23 strong line method. The
absolute B-band magnitudes of the galaxies span -20.6 < M_B < -18.3. If the
metallicities lie on the R23 upper branch (8.4 < log (O/H) + 12 < 8.9), then
the metallicities of these absorption selected galaxies span the range between
0.5--1.4 solar and would be consistent with the well-known
luminosity-metallicity relation for 0.10 < z < 0.45 emission-line galaxies.
However, such metallicities would be 0.5--1.0 dex higher than those observed in
damped Lyman alpha systems (DLAs) via absorption line measurements at similar
redshifts. Conversely, the lower R23 branch calibration yields metallicities
approximately 1/7 solar, consistent with the DLA absorption metallicities at
low redshifts. In this case, the absorption selected galaxies would lie
significantly lower than the luminosity-metallicity relation for emission-line
galaxies at z<0.5. We discuss the implications and possible solutions for each
scenario.

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The categories of this paper are: physics
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The categories of this paper are: atom-ph
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The categories of this paper are: funct-an
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The categories of this paper are: hep-lat
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The categories of this paper are: q-fin
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The categories of this paper are: math-ph
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The categories of this paper are: q-alg
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The categories of this paper are: ao-sci
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The categories of this paper are: hep-ex
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The categories of this paper are: chao-dyn
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The categories of this paper are: alg-geom
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The categories of this paper are: mtrl-th
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The categories of this paper are: q-bio
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The categories of this paper are: gr-qc
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The categories of this paper are: nucl-ex
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The categories of this paper are: chem-ph