Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Soft X-Ray Sources at the Centers of the Elliptical Galaxies NGC 4472
  and NGC 4649   Analysis of recent Chandra observations of the elliptical galaxies NGC 4472
and NGC 4649 has revealed faint soft X-ray sources at their centers. The
sources are located to within 1'' of the optical centers of the galaxies. They
are most likely associated with the central supermassive black holes. Interest
in these and several other similar objects stems from the unusually low
luminosity of the supermassive black holes embedded in dense interstellar
medium. Our Chandra sources have very soft spectra. They are detectable only
below ~0.6 keV and have luminosities in the 0.2-2.5 keV energy band of ~ 6 *
10^{37} erg/s and ~1.7 * 10^{38} erg/s in NGC 4649 and NGC 4472, respectively.

17
The categories of this paper are: q-fin
22
The categories of this paper are: chao-dyn
2
The categories of this paper are: math
34
The categories of this paper are: chem-ph
23
The categories of this paper are: solv-int
8
The categories of this paper are: hep-ex
29
The categories of this paper are: funct-an
4
The categories of this paper are: cond-mat
35
The categories of this paper are: mtrl-th
28
The categories of this paper are: alg-geom
21
The categories of this paper are: adap-org
30
The categories of this paper are: q-alg
1
The categories of this paper are: cs
3
The categories of this paper are: physics
27
The categories of this paper are: comp-gas
24
The categories of this paper are: dg-ga