Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: ALFALFA Discovery of the Most Metal-Poor Gas-Rich Galaxy Known: AGC
  198691   We present spectroscopic observations of the nearby dwarf galaxy AGC 198691.
This object is part of the Survey of HI in Extremely Low-Mass Dwarfs (SHIELD)
project, which is a multi-wavelength study of galaxies with HI masses in the
range of 10$^{6}$-10$^{7.2}$~M$_{\odot}$ discovered by the ALFALFA survey. We
have obtained spectra of the lone HII region in AGC 198691 with the new
high-throughput KPNO Ohio State Multi-Object Spectrograph (KOSMOS) on the
Mayall 4-m as well as with the Blue Channel spectrograph on the MMT 6.5-m
telescope. These observations enable the measurement of the
temperature-sensitive [OIII]$\lambda$4363 line and hence the determination of a
"direct" oxygen abundance for AGC 198691. We find this system to be an
extremely metal-deficient (XMD) system with an oxygen abundance of 12+log(O/H)
= 7.02 $\pm$ 0.03, making AGC 198691 the lowest-abundance star-forming galaxy
known in the local universe. Two of the five lowest-abundance galaxies known
have been discovered by the ALFALFA blind HI survey; this high yield of XMD
galaxies represents a paradigm shift in the search for extremely metal-poor
galaxies.

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The categories of this paper are: gr-qc
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The categories of this paper are: stat
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The categories of this paper are: nucl-th
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The categories of this paper are: nlin
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The categories of this paper are: alg-geom
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The categories of this paper are: patt-sol
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The categories of this paper are: cs
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The categories of this paper are: q-fin
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The categories of this paper are: hep-ex
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The categories of this paper are: bayes-an
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The categories of this paper are: physics
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The categories of this paper are: solv-int
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The categories of this paper are: hep-lat
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The categories of this paper are: adap-org
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The categories of this paper are: ao-sci
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The categories of this paper are: q-bio