Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the apparent coupling of neutral hydrogen and dark matter in spiral
  galaxies   We have studied a mass model for spiral galaxies in which the dark matter
surface density is a scaled version of the observed HI surface density.
Applying this mass model to a sample of 24 spiral galaxies with reliable
rotation curves one obtains good fits for most galaxies. The scaling factors
cluster around 7, after correction for the presence of primordial helium. But
for several cases different, often larger, values are found. For galaxies that
can not be fitted well the discrepancy occurs at large radii and results from a
fairly rapid decline of the HI surface density in the outermost regions.
Because of such imperfections and in view of possible selection effects it is
not possible to conclude here that there is a real coupling between HI and dark
matter in spiral galaxies.

3
The categories of this paper are: physics
34
The categories of this paper are: chem-ph
26
The categories of this paper are: bayes-an
2
The categories of this paper are: math
8
The categories of this paper are: hep-ex
31
The categories of this paper are: ao-sci
7
The categories of this paper are: hep-th
29
The categories of this paper are: funct-an
1
The categories of this paper are: cs
22
The categories of this paper are: chao-dyn
13
The categories of this paper are: quant-ph
9
The categories of this paper are: nlin
12
The categories of this paper are: nucl-th
14
The categories of this paper are: math-ph
36
The categories of this paper are: cmp-lg
21
The categories of this paper are: adap-org