Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Role of Pressure in GMC Formation   We examine the hypothesis that hydrostatic pressure alone determines the
ratio of atomic to molecular gas averaged over a particular radius in disk
galaxies. The hypothesis implies that the transition radius, the location where
the ratio is unity, should always occur at the same value of stellar surface
density in all galaxies. We examine data for 28 galaxies and find that the
stellar surface density at the transition radius is indeed constant to 40% at a
value of 120 M_sun/pc^2. If the hypothesis can be confirmed at all radii within
a large range of galaxy types and metallicities, combining it with the observed
constancy of the star formation rate with H_2 surface density may enable a
physically motivated star formation prescription with wide applicability.

11
The categories of this paper are: hep-lat
35
The categories of this paper are: mtrl-th
4
The categories of this paper are: cond-mat
13
The categories of this paper are: quant-ph
5
The categories of this paper are: gr-qc
34
The categories of this paper are: chem-ph
27
The categories of this paper are: comp-gas
2
The categories of this paper are: math
1
The categories of this paper are: cs
20
The categories of this paper are: acc-phys
14
The categories of this paper are: math-ph
36
The categories of this paper are: cmp-lg
22
The categories of this paper are: chao-dyn
23
The categories of this paper are: solv-int
9
The categories of this paper are: nlin
32
The categories of this paper are: atom-ph