Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Curious Case of NGC6908   The object NGC6908 was once thought to be simply a surface-brightness
enhancement in the eastern spiral arm of the nearby spiral galaxy NGC6907.
Based on an examination of near-infrared imaging, the object is shown in fact
to be a lenticular S0(6/7) galaxy hidden in the optical glare of the disk and
spiral structure of the larger galaxy. New radial velocities of NGC6908
(3,060+/-16 (emission); 3,113+/-73 km/s (absorption)) have been obtained at the
Baade 6.5m and the duPont 2.5m telescopes at Las Campanas, Chile placing
NGC6908 at the same expansion-velocity distance as NGC6907 (3,190+/-5 km/s),
eliminating the possibility of a purely chance line-of-sight coincidence. The
once-enigmatic asymmetries in the disk and outer spiral structure of NGC6907
are now explained as being due to an advanced merger event. Newly discovered
tails and debris in the outer reaches of this galaxy further support the merger
scenario for this system. This pair of galaxies is a rather striking example of
two objects discovered over 100 years ago, whose true nature was lost until
modern detectors operating at infrared wavelengths gave us a new
(high-contrast) look. Other examples of embedded merger remnants may also
reveal themselves in the growing samples of near-infrared imaging of nearby
galaxies; and a pilot study does reveal several other promising candidates for
follow-up observations.

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The categories of this paper are: hep-lat
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The categories of this paper are: dg-ga
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The categories of this paper are: funct-an
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The categories of this paper are: q-alg
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The categories of this paper are: adap-org
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The categories of this paper are: cmp-lg
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The categories of this paper are: nlin
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The categories of this paper are: physics
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The categories of this paper are: plasm-ph
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The categories of this paper are: hep-th
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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: econ
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The categories of this paper are: hep-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: math