Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Unveiling Dust-enshrouded Star Formation in the Early Universe: a Sub-mm
  Survey of the Hubble Deep Field   The advent of sensitive sub-mm array cameras now allows a proper census of
dust-enshrouded massive star-formation in very distant galaxies, previously
hidden activity to which even the faintest optical images are insensitive. We
present the deepest sub-mm survey of the sky to date, taken with the SCUBA
camera on the James Clerk Maxwell Telescope and centred on the Hubble Deep
Field. The high source density found in this image implies that the survey is
confusion-limited below a flux density of 2 mJy. However, within the central 80
arcsec radius independent analyses yield 5 reproducible sources with S(850um) >
2 mJy which simulations indicate can be ascribed to individual galaxies. We
give positions and flux densities for these, and furthermore show using
multi-frequency photometric data that the brightest sources in our map lie at
redshifts z~3. These results lead to integral source counts which are
completely inconsistent with a no-evolution model, and imply that massive
star-formation activity continues at redshifts > 2. The combined brightness of
the 5 most secure sources in our map is sufficient to account for 30 - 50% of
the previously unresolved sub-mm background, and we estimate statistically that
the entire background is resolved at about the 0.3 mJy level. Finally we
discuss possible optical identifications and redshift estimates for the
brightest sources. One source appears to be associated with an extreme
starburst galaxy at z~1, whilst the remaining four appear to lie in the
redshift range 2 < z < 4. This implies a star-formation density over this
redshift range that is at least five times higher than that inferred from the
ultraviolet output of HDF galaxies.

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The categories of this paper are: adap-org
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The categories of this paper are: gr-qc
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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: nucl-th
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The categories of this paper are: q-alg
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The categories of this paper are: funct-an
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The categories of this paper are: nucl-ex
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The categories of this paper are: math-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: alg-geom
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The categories of this paper are: cmp-lg
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-ph
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The categories of this paper are: solv-int
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The categories of this paper are: ao-sci