Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Observations and models of the embedded phase of high-mass star
  formation   This paper is a review and an update on recent work on the physical and
chemical structure of the envelopes of newly born massive stars, at the stages
preceding ultracompact H II regions. It discusses methods and results to
determine total mass, temperature and density structure, ionization rate, and
depth-dependent chemical composition.

24
The categories of this paper are: dg-ga
23
The categories of this paper are: solv-int
4
The categories of this paper are: cond-mat
22
The categories of this paper are: chao-dyn
21
The categories of this paper are: adap-org
9
The categories of this paper are: nlin
7
The categories of this paper are: hep-th
2
The categories of this paper are: math
16
The categories of this paper are: stat
3
The categories of this paper are: physics
11
The categories of this paper are: hep-lat
13
The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th
14
The categories of this paper are: math-ph
31
The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas