Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The HI absorption "Zoo"   We present an analysis of the HI absorption in a sample of 101 flux-selected
radio AGN (S_1.4 GHz > 50 mJy) observed with the Westerbork Synthesis Radio
Telescope (WSRT). HI absorption is detected in 32 galaxies, showing a broad
variety of widths, shapes and kinematical properties. We characterize the HI
spectra of the individual detections using the busy function (Westmeier et al.
2014).
  With the goal of identifying different morphological structures of HI, we
study the kinematical and radio source properties of the detections as function
of their width. Narrow lines (FWHM < 100 km/s) mostly lie at the systemic
velocity and are likely produced by regularly rotating HI disks or clouds. More
HI disks can be present among galaxies with lines of intermediate widths (100
km/s < FWHM < 200 km/s), however the HI in these sources is more unsettled.
  We study the asymmetry parameter and blueshift/redshift distribution of the
lines. We argue that if a profile is broad, it is also asymmetric and shifted
relative to the systemic velocity because it is tracing unsettled HI gas.
Besides three of the broadest (up to FW20 = 825 km/s) detections, which are
associated with gas-rich mergers, we find three new cases of blueshifted broad
wings (with FW20 >= 500 km/s). These detections are good candidates for being
HI outflows. The detection rate of HI outflows is 5 percent in the total radio
AGN sample. This fraction represents a lower limit, however it could suggests
that, if outflows are a characteristic phenomenon of all radio sources, they
would have a short depletion timescale compared to the lifetime of the AGN.
  Blueshifted and broad/asymmetric lines are more often present among young,
compact sources, suggesting that in these AGN the HI is likely to be unsettled.
This may arise due to jet-cloud interactions, as young radio sources clear
their way through the rich ambient gaseous medium.

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The categories of this paper are: hep-ph
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The categories of this paper are: physics
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-ex
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The categories of this paper are: plasm-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: comp-gas
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The categories of this paper are: atom-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: supr-con
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The categories of this paper are: hep-th
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The categories of this paper are: acc-phys
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The categories of this paper are: mtrl-th
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The categories of this paper are: q-fin
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The categories of this paper are: cs
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The categories of this paper are: funct-an