Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spiral and Bar Instabilities Provoked by Dark Matter Satellites   We explore the secular dynamical evolution of an N-body model of M31 in the
presence of a population of 100 dark matter satellites over 10 Gyr. The
satellite population has structural and kinematic characteristics modelled to
follow the predictions of Lambda-CDM cosmological simulations. Vertical disk
heating is a small effect despite many interactions with the satellite
population with only a 20% increase in vertical velocity dispersion sigma_z and
the disk scale height z_d at the equivalent solar radius R = 2.5R_d . However,
the stellar disk is noticeably flared after 10 Gyr with z_d nearly doubling at
the disk edge. Azimuthal disk heating is much larger with sigma_R and sigma_z
both increasing by 1.7x. However, in a control experiment without satellites
dispersion increases by 1.5x suggesting that most of the effect is due to
heating through scattering off of spiral structure excited by swing-amplified
noise. Surprisingly, direct impacts of satellites on the disk can excite spiral
structure with a significant amplitude and in some cases impacts close to the
disk center also induce the bar instability. The large number of dark matter
satellite impacts expected over a galaxy's lifetime may be a significant source
of external perturbations for driving disk secular evolution.

8
The categories of this paper are: hep-ex
28
The categories of this paper are: alg-geom
0
The categories of this paper are: hep-ph
31
The categories of this paper are: ao-sci
13
The categories of this paper are: quant-ph
15
The categories of this paper are: nucl-ex
32
The categories of this paper are: atom-ph
25
The categories of this paper are: patt-sol
12
The categories of this paper are: nucl-th
4
The categories of this paper are: cond-mat
20
The categories of this paper are: acc-phys
9
The categories of this paper are: nlin
21
The categories of this paper are: adap-org
30
The categories of this paper are: q-alg
26
The categories of this paper are: bayes-an
19
The categories of this paper are: eess