Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Complex Mid-Infrared Structure at the Heart of IRAS 20126+4104   The mid-infrared emission at the center of IRAS 21026+4104 is not that of a
simple compact source, as one would expect from an isolated high mass
protostellar object. Furthermore the central thermal infrared emission does not
appear to be coming directly from a circumstellar disk as has been recently
hypothesized from near-infrared observations. The mid-infrared structure is
complex, but with the help of multiple wavelength information two plausible
scenarios to explain the emission in the region are advanced. The first is that
there is a tight cluster of young stellar objects here. The second is that the
mid-infrared emission and masers are delineating the walls of the outflow
cavities of a massive stellar source located in the center of the near- and
mid-infrared dark lane.

9
The categories of this paper are: nlin
3
The categories of this paper are: physics
28
The categories of this paper are: alg-geom
36
The categories of this paper are: cmp-lg
21
The categories of this paper are: adap-org
35
The categories of this paper are: mtrl-th
7
The categories of this paper are: hep-th
33
The categories of this paper are: plasm-ph
37
The categories of this paper are: supr-con
17
The categories of this paper are: q-fin
12
The categories of this paper are: nucl-th
11
The categories of this paper are: hep-lat
2
The categories of this paper are: math
31
The categories of this paper are: ao-sci
32
The categories of this paper are: atom-ph
34
The categories of this paper are: chem-ph