Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A sensitive search for CO J=1-0 emission in 4C 41.17: high-excitation
  molecular gas at z=3.8   We report sensitive imaging observations of the CO J=1-0 line emission in the
powerful high-redshift radio galaxy 4C 41.17 (z=3.8) with the NRAO Very Large
Array (VLA), conducted in order to detect the large concomitant H_2 gas
reservoir recently unveiled in this system by De Breuck et al (2005) via the
emission of the high excitation J=4-3 line. Our observations fail to detect the
J=1-0 line but yield sensitive lower limits on the R_43=(4-3)/(1-0) brightness
temperature ratio of R_43 ~ 0.55 - >1.0 for the bulk of the H_2 gas mass. Such
high ratios are typical of the high-excitation molecular gas phase ``fueling''
the star formation in local starbursts, but quite unlike these objects, much of
the molecular gas in 4C 41.17 seems to be in such a state, and thus
participating in the observed starburst episode. The widely observed and unique
association of highly excited molecular gas with star forming sites allows CO
line emission with large (high-J)/(low-J) intensity ratios to serve as an
excellent ``marker'' of the spatial distribution of star formation in distant
dust-obscured starbursts, unaffected by extinction.

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The categories of this paper are: alg-geom
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The categories of this paper are: solv-int
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The categories of this paper are: dg-ga
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The categories of this paper are: funct-an
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The categories of this paper are: ao-sci
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The categories of this paper are: q-alg
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The categories of this paper are: chem-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: chao-dyn
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-lat
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The categories of this paper are: q-fin
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The categories of this paper are: cond-mat
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The categories of this paper are: math-ph
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The categories of this paper are: physics