Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Keck Deep Fields. II. The UV Galaxy Luminosity Function at z~4, 3, and 2   We use very deep UGRI multi-field imaging obtained at the Keck telescope to
study the evolution of the rest-frame 1700A galaxy luminosity function as the
Universe doubles its age from z~4 to z~2. The depth of our imaging allows us to
constrain the faint end of the luminosity function reaching M_1700A ~ -18.5 at
z~3 (equivalent to ~1M_sun/yr) accounting for both N^1/2 uncertainty in the
number of galaxies and for cosmic variance. We carefully examine many potential
sources of systematic bias in our LF measurements before drawing the following
conclusions. We find that the luminosity function of Lyman Break Galaxies
evolves with time and that this evolution is likely differential with
luminosity. The result is best constrained between the epochs at z~4 and z~3,
where we find that the number density of sub-L* galaxies increases with time by
at least a factor of 2.3 (11sigma statistical confidence); while the faint end
of the LF evolves, the bright end appears to remain virtually unchanged,
indicating that there may be differential, luminosity-dependent evolution
significant at the 97% level. Potential systematic biases restric our ability
to draw strong conclusions about continued evolution of the luminosity function
to lower redshifts, z~2.2 and z~1.7, but, nevertheless, it appears certain that
the number density of z~2.2 galaxies at all luminosities we studied,
-22<M_1700A<-18, is at least as high as that of their counterparts at z~3.
While it is not yet clear what mechanism underlies the observed evolution, the
fact that this evolution is differential with luminosity opens up new avenues
of improving our understanding of how galaxies form and evolve at high
redshift.

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The categories of this paper are: q-bio
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The categories of this paper are: chao-dyn
2
The categories of this paper are: math
31
The categories of this paper are: ao-sci
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The categories of this paper are: atom-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: cs
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The categories of this paper are: q-fin
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The categories of this paper are: math-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: alg-geom
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-th
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-ph
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The categories of this paper are: plasm-ph