Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: HI 21cm observations of the PG1216+069 sub-DLy-alpha absorber field at
  z=0.00632   The Westerbork Synthesis Radio Telescope finds a weak 21cm line emission
feature at the coordinates (RA-Dec-velocity) of the sub-Damped Lyman-alpha
absorber observed at z_abs=0.00632 in the spectrum of PG1216+069. The emission
feature, WSRT-J121921+0639, lies within 30" of the quasar sightline, is
detected at 99.8% (3 sigma) confidence level, has M_HI between 5 and 15x10^6
M_solar, and has velocity spread between 20 and 60 km/s. Other HI emitters in
the field include VCC297 at a projected distance of 86/h_75 kpc and a
previously unreported HI cloud, WSRT-J121919+0624 at 112/h_75 kpc with M_HI ~
3x10^8 M_solar. The optically identified, foreground galaxy that is closest to
the quasar sightline appears to be VCC339 (~L*/25) at 29/h_75 kpc and velocity
offset 292 km/s . A low surface brightness galaxy with the HI mass of the
sub-DLA absorber WSRT-J121921+0639 would likely have m_B ~ 17, and its diffuse
optical emission would need to compete with the light of both the background
QSO and a brighter foreground star ~10" from the QSO sight line.

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The categories of this paper are: math-ph
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The categories of this paper are: q-alg
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The categories of this paper are: gr-qc
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The categories of this paper are: cond-mat
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The categories of this paper are: hep-th
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The categories of this paper are: plasm-ph
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The categories of this paper are: adap-org
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The categories of this paper are: alg-geom
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The categories of this paper are: nlin
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The categories of this paper are: comp-gas
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The categories of this paper are: hep-ph
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The categories of this paper are: cs
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The categories of this paper are: hep-lat
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The categories of this paper are: quant-ph
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The categories of this paper are: econ
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The categories of this paper are: supr-con