Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Stars & Gas in the Galaxy Pair II Zw 70/71   II Zw 71 (UGC 9562) was classified as a ``probable'' polar-ring galaxy in the
Polar-Ring Catalog, based upon its optical appearance. We present 21 cm and
optical observations of this galaxy and its companion, the blue star-forming
dwarf II Zw 70. Our 21 cm observations show that 5e8 solar masses of HI is
present in a polar ring orbiting II Zw 71, and show a spatially and
kinematically contiguous streamer with 2.5e8 solar masses of HI gas between the
two galaxies. This gaseous bridge, plus our observations of Halpha line
emission in the polar ring and in II Zw 70, are strong evidence for an ongoing
interaction between the two galaxies. However, the configuration of the
streamer suggests that the polar ring itself may well have predated the current
interaction, which then stimulated an outburst of star formation in the ring
gas.

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The categories of this paper are: econ
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The categories of this paper are: q-fin
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The categories of this paper are: nucl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: chao-dyn
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The categories of this paper are: cmp-lg
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The categories of this paper are: q-bio
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The categories of this paper are: nlin
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The categories of this paper are: hep-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: nucl-ex
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The categories of this paper are: ao-sci
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The categories of this paper are: stat
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The categories of this paper are: atom-ph
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The categories of this paper are: eess
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The categories of this paper are: funct-an