Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: First Detection of Molecular Gas in the Shells of CenA   Shells are faint arc-like stellar structures, which have been observed around
early type galaxies and are thought to be the result of an interaction. HI gas
has recently been detected in shells, a surprising result in view of the
theoretical predictions that most of the gas should decouple from stars and
fall into the nucleus in such interactions. Here we report the first detection
of molecular gas (CO) in shells, found 15kpc away from the center of NGC5128
(CenA), a giant elliptical galaxy that harbors an active nucleus (AGN). The
ratio between CO and HI emission in the shells is the same as that found in the
central regions, which is unexpected given the metallicity gradient usually
observed in galaxies. We propose that the dynamics of the gas can be understood
within the standard picture of shell formation if one takes into account that
the interstellar medium is clumpy and hence not highly dissipative. The
observed metal enrichment could be due to star formation induced by the AGN jet
in the shells. Furthermore our observations provide evidence that molecular gas
in mergers may be spread out far from the nuclear regions.

13
The categories of this paper are: quant-ph
17
The categories of this paper are: q-fin
14
The categories of this paper are: math-ph
19
The categories of this paper are: eess
12
The categories of this paper are: nucl-th
24
The categories of this paper are: dg-ga
31
The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas
1
The categories of this paper are: cs
25
The categories of this paper are: patt-sol
9
The categories of this paper are: nlin
33
The categories of this paper are: plasm-ph
3
The categories of this paper are: physics
15
The categories of this paper are: nucl-ex
37
The categories of this paper are: supr-con
29
The categories of this paper are: funct-an