Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The blue host galaxy of the red GRB 000418   We report on multi-band (UBVRIZJsKs) observations of the host galaxy of the
April 18, 2000 gamma-ray burst. The Spectral Energy Distribution (SED) is
analysed by fitting empirical and synthetic spectral templates. We find that:
(i) the best SED fit is obtained with a starburst template, (ii) the
photometric redshift is consistent with the spectroscopic redshift, (iii) the
colours of the host are inconsistent with an old stellar population, and (iv)
the global extinction is constrained to be in the range Av=0.12-0.61 mag. The
derived global extinction agrees with the one reported for the afterglow
(Av=0.4-0.9 mag), suggesting a homogeneous distribution of the interstellar
medium (ISM) in the host galaxy. These findings are supplemented by
morphological information from Hubble Space Telescope (HST) imaging: the
surface brightness profile is smooth, symmetric and compact with no underlying
structures (like dust lanes, spiral arms or disks). A natural scenario which
accounts of all the above results is a nuclear starburst that harbours a young
population of stars from which the GRB originated.

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The categories of this paper are: q-fin
0
The categories of this paper are: hep-ph
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The categories of this paper are: econ
34
The categories of this paper are: chem-ph
4
The categories of this paper are: cond-mat
35
The categories of this paper are: mtrl-th
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The categories of this paper are: hep-ex
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The categories of this paper are: chao-dyn
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The categories of this paper are: acc-phys
3
The categories of this paper are: physics
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The categories of this paper are: math-ph
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The categories of this paper are: solv-int
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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: math
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The categories of this paper are: cmp-lg