Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Astrochemistry at work in the L1157-B1 shock: acetaldehyde formation   The formation of complex organic molecules (COMs) in protostellar
environments is a hotly debated topic. In particular, the relative importance
of the gas phase processes as compared to a direct formation of COMs on the
dust grain surfaces is so far unknown. We report here the first high-resolution
images of acetaldehyde (CH$_3$CHO) emission towards the chemically rich
protostellar shock L1157-B1, obtained at 2 mm with the IRAM Plateau de Bure
interferometer. Six blueshifted CH$_3$CHO lines with $E_{\rm u}$ = 26-35 K have
been detected. The acetaldehyde spatial distribution follows the young ($\sim$
2000 yr) outflow cavity produced by the impact of the jet with the ambient
medium, indicating that this COM is closely associated with the region enriched
by iced species evaporated from dust mantles and released into the gas phase. A
high CH$_3$CHO relative abundance, 2-3 $\times$ 10$^{-8}$, is inferred,
similarly to what found in hot-corinos. Astrochemical modelling indicates that
gas phase reactions can produce the observed quantity of acetaldehyde only if a
large fraction of carbon, of the order of 0.1%, is locked into iced
hydrocarbons.

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The categories of this paper are: adap-org
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The categories of this paper are: stat
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The categories of this paper are: acc-phys
26
The categories of this paper are: bayes-an
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The categories of this paper are: q-bio
4
The categories of this paper are: cond-mat
33
The categories of this paper are: plasm-ph
3
The categories of this paper are: physics
28
The categories of this paper are: alg-geom
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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: dg-ga
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The categories of this paper are: supr-con
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The categories of this paper are: math
0
The categories of this paper are: hep-ph
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The categories of this paper are: chao-dyn