Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: NGC 90: a hidden jelly-fish galaxy?   We study a peculiar galaxy NGC 90, a pair member of interacting system Arp 65
(NGC 90/93), using the long-slit spectral observations carried out at the
Russian 6m telescope BTA and the available SDSS photometric data. This galaxy
demonstrates two tidal tails containing young stellar population, being an
extension of its `Grand Design' spiral arms. We obtained the distribution of
velocity and oxygen abundance of emission gas (O/H) for two slit orientations.
In the central part of the galaxy a significant role belongs to
non-photoionization mechanism of line emission probably caused by shocks due to
LINER-like activity of the nucleus. The O/H has a shallow abundance gradient,
typical for interacting galaxies. The most intriguing peculiarity of the galaxy
is the presence of the discovered earlier huge HI `cloud' containing about half
of total mass of galaxy gas, which is strongly displaced outwards and has a
velocity exceeding at about 340 km/s the central velocity of the main galaxy.
We found traces of current star formation in the `cloud', even though the cloud
is apparently not gravitationally bound with the galaxy. A possible nature of
the `cloud' is discussed. We argue that it presents a flow of gas sweeping by
ram pressure and elongated along a line of sight.

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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: math
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The categories of this paper are: math-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: chem-ph
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The categories of this paper are: cs
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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: mtrl-th
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The categories of this paper are: adap-org
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The categories of this paper are: eess
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The categories of this paper are: nlin
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The categories of this paper are: q-fin
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The categories of this paper are: chao-dyn
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The categories of this paper are: econ