Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Deep Ly-alpha imaging of two z=2.04 GRB host galaxy fields   We report on the results of deep narrow-band Ly-alpha, U and I imaging of the
fields of two GRBs at z=2.04 (GRB 000301C and GRB 000926). We find that the
host galaxy of GRB 000926 is an extended, strong Ly-alpha emitter with a
rest-frame equivalent width of 71+20-15 AA. The galaxy consists of two main
components and several fainter knots. GRB 000926 occurred in the western
component, whereas most of the Ly-alpha luminosity (about 65%) originates in
the eastern component. Using archival HST images of the host galaxy we measure
the spectral slopes (f_lambda prop. to lambda^beta) of the two components to
beta = -2.4+-0.3 (east) and -1.4+-0.2 (west). This implies that both components
contain at most small amounts of dust, consistent with the observed strong
Ly-alpha emission. The western component has a slightly redder V-I colour than
the eastern component, suggesting the presence of at least some dust. We do not
detect the host galaxy of GRB 000301C in neither Ly-alpha emission nor in U and
I-band images. We infer a limit of U(AB)>27.7 (2-sigma limit per arcsec^2). The
upper limits on the Ly-alpha flux implies a Ly-alpha equivalent width upper
limit of 150AA. We find 11 and 8 other galaxies with excess emission in the
narrow filter in the fields of GRB 000301C and GRB 000926 respectively. Based
on these detections we conclude that GRB 000926 occurred in one of the
strongest centres of star formation within several Mpc, whereas GRB 000301C
occurred in an intrinsically very faint galaxy far from being the strongest
centre of star formation in its galactic environment. Under the hypothesis that
GRBs trace star formation, the wide range of GRB host galaxy luminosities
implies a very steep faint end slope of the high redshift galaxy luminosity
function.

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The categories of this paper are: econ
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The categories of this paper are: dg-ga
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The categories of this paper are: eess
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The categories of this paper are: q-alg
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The categories of this paper are: hep-th
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The categories of this paper are: atom-ph
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The categories of this paper are: nlin
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The categories of this paper are: cmp-lg
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The categories of this paper are: bayes-an
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The categories of this paper are: math
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-ex
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The categories of this paper are: comp-gas
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The categories of this paper are: chem-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: nucl-ex