Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The evolution of the surface brightness of a star cluster as a result of
  residual star-forming gas expulsion   Direct N-body calculations are presented of the early evolution of exposed
clusters to quantify the influence of gas expulsion on the time-varying surface
brightness. By assuming that the embedded OB stars drive out most of the gas
after a given time delay, the change of the surface brightness of expanding
star clusters is studied. The influence of stellar dynamics and stellar
evolution is discussed. The growth of the core radii of such models shows a
remarkable core re-virialisation. The decrease of the surface mass density
during gas expulsion is large and is only truncated by this re-virialisation
process. However, the surface brightness within a certain radius does not
increase noticeably. Thus, an embedded star cluster cannot reappear in
observational surveys after re-virialisation. This finding has a bearing on the
observed infant mortality fraction.

9
The categories of this paper are: nlin
1
The categories of this paper are: cs
10
The categories of this paper are: q-bio
28
The categories of this paper are: alg-geom
35
The categories of this paper are: mtrl-th
37
The categories of this paper are: supr-con
32
The categories of this paper are: atom-ph
16
The categories of this paper are: stat
5
The categories of this paper are: gr-qc
27
The categories of this paper are: comp-gas
29
The categories of this paper are: funct-an
34
The categories of this paper are: chem-ph
8
The categories of this paper are: hep-ex
15
The categories of this paper are: nucl-ex
26
The categories of this paper are: bayes-an
22
The categories of this paper are: chao-dyn