Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Near-Infrared Search for Line Emission from Protogalaxies Using the W.
  M. Keck Telescope   We present the first results from a near-infrared narrow-band search for
primeval galaxies (PGs) using the Keck 10~m telescope. We have targeted our
fields for three QSOs and one radio galaxy at redshifts $z = 2.28$ to $4.70$.
We selected narrow-band filters in the $K$-band centered on strong emision
lines at the redshift of the targets. We reach limiting fluxes between
$1.6\times 10^{-17}$~erg~s$^{-1}$~cm$^{-2}$ and $1.0\times
10^{-16}$~erg~s$^{-1}$~cm$^{-2}$, and cover a total area of $\sim
4$~arcmin$^2$. At the redshifts of interest, these flux limits correspond to
typical restframe line luminosities of $\sim 10^{42} - 10^{43}$~erg~s$^{-1}$,
unobscured star formation rates of $\sim 1 - 100$ $M_\odot$~yr$^{-1}$, and a
sampled comoving volume of several tens of Mpc$^3$. We have found no candidate
PGs at a $2\sigma$ confidence level. We demonstrate that for moderate dust
absorption ($A_V \gsim 2^m$) in a simple dust-screen model, our preliminary
survey puts a strong constraint on intrinsic PG luminosities during an intial
burst of star formation. In the case of the QSOs, we have used PSF-subtraction
to search for the presence of faint, extended line emission surrounding these
radio-quiet AGNs. We find no evidence for extended emission down to $3.7 \times
10^{-17}$~erg~s$^{-1}$~cm$^{-2}$. This imposes limits on the reprocessed
fraction of the QSO continuum emission ranging between $0.02$\% and $0.29$\%;
if beaming effects are not important, then this implies similarly small
covering factors for clouds optically thick to the QSO continuum emission.

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The categories of this paper are: mtrl-th
4
The categories of this paper are: cond-mat
14
The categories of this paper are: math-ph
11
The categories of this paper are: hep-lat
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The categories of this paper are: q-alg
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The categories of this paper are: nlin
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The categories of this paper are: patt-sol
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The categories of this paper are: atom-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: stat
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The categories of this paper are: acc-phys
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The categories of this paper are: econ
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The categories of this paper are: hep-th
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The categories of this paper are: cmp-lg
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The categories of this paper are: quant-ph