Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Near-infrared and X-ray obscuration to the nucleus of the Seyfert 2
  galaxy NGC 3281   We present the results of a near-infrared and X-ray study of the Seyfert 2
galaxy NGC 3281. Emission from the Seyfert nucleus is detected in both regions
of the electromagnetic spectrum, allowing us to infer both the equivalent line
of sight hydrogen column density, N_H = 71.0(+11.3,-12.3)e26/m^2 and the
extinction due to dust, A_V = 22+/-11 magnitudes (90% confidence intervals). We
infer a ratio of N_H/A_V which is an order of magnitude larger than that
determined along lines of sight in the Milky Way and discuss possible
interpretations. We consider the most plausible explanation to be a dense cloud
in the foreground of both the X-ray and infrared emitting regions which
obscures the entire X-ray source but only a fraction of the much larger
infrared source.

12
The categories of this paper are: nucl-th
18
The categories of this paper are: econ
33
The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio
19
The categories of this paper are: eess
27
The categories of this paper are: comp-gas
16
The categories of this paper are: stat
9
The categories of this paper are: nlin
36
The categories of this paper are: cmp-lg
26
The categories of this paper are: bayes-an
17
The categories of this paper are: q-fin
14
The categories of this paper are: math-ph
25
The categories of this paper are: patt-sol
8
The categories of this paper are: hep-ex
34
The categories of this paper are: chem-ph
7
The categories of this paper are: hep-th