Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Understanding the Nuclear Gas Dispersion in Early-Type Galaxies in the
  Context of Black Hole Demographics   (abridged) We analyze and model HST /STIS observations of a sample of 27
galaxies; 16 Fanaroff & Riley Type I radio galaxies and 11 (more) normal
early-type galaxies. We focus here on what can be learned from the nuclear
velocity dispersion (line width) of the gas as a complement to the many studies
dealing with gas rotation velocities. We find that the dispersion in a STIS
aperture of ~0.1''-0.2'' generally exceeds the large-scale stellar velocity
dispersion of the galaxy. This is qualitatively consistent with the presence of
central BHs, but raises the question whether the excess gas dispersion is of
gravitational or non-gravitational origin and whether the implied BH masses are
consistent with our current understanding of BH demography(as predicted by the
M-sigma relation between BH mass and stellar velocity dispersion). To address
this we construct dynamical models for the gas, both thin disk models and
models with more general axis ratios and velocity anisotropies. For the normal
galaxies the nuclear gas dispersions are adequately reproduced assuming disks
around BHs with masses that follow the M-sigma relation. In contrast, the gas
dispersions observed for the radio galaxies generally exceed those predicted by
any of the models. We attribute this to the presence of non-gravitational
motions in the gas that are similar to or larger than the gravitational
motions. The non- gravitational motions are presumably driven by the active
galactic nucleus (AGN), but we do not find a relation between the radiative
output of the AGN and the non-gravitational dispersion. It is not possible to
uniquely determine the BH mass for each galaxy from its nuclear gas dispersion.
However, for the sample as a whole the observed dispersions do not provide
evidence for significant deviations from the M-sigma relation.

27
The categories of this paper are: comp-gas
16
The categories of this paper are: stat
23
The categories of this paper are: solv-int
20
The categories of this paper are: acc-phys
32
The categories of this paper are: atom-ph
10
The categories of this paper are: q-bio
21
The categories of this paper are: adap-org
34
The categories of this paper are: chem-ph
28
The categories of this paper are: alg-geom
8
The categories of this paper are: hep-ex
12
The categories of this paper are: nucl-th
0
The categories of this paper are: hep-ph
13
The categories of this paper are: quant-ph
17
The categories of this paper are: q-fin
5
The categories of this paper are: gr-qc
9
The categories of this paper are: nlin