1,794 research outputs found
Bending instability in galactic discs. Advocacy of the linear theory
We demonstrate that in N-body simulations of isolated disc galaxies there is
numerical vertical heating which slowly increases the vertical velocity
dispersion and the disc thickness. Even for models with over a million
particles in a disc, this heating can be significant. Such an effect is just
the same as in numerical experiments by Sellwood (2013). We also show that in a
stellar disc, outside a boxy/peanut bulge, if it presents, the saturation level
of the bending instability is rather close to the value predicted by the linear
theory. We pay attention to the fact that the bending instability develops and
decays very fast, so it couldn't play any role in secular vertical heating.
However the bending instability defines the minimal value of the ratio between
the vertical and radial velocity dispersions
(so indirectly the minimal thickness) which could have stellar discs in real
galaxies. We demonstrate that observations confirm last statement.Comment: 8 pages, 8 figures, accepted for publication in MNRA
Metallicity-dependendent kinematics and morphology of the Milky Way bulge
We use N-body chemo-dynamic simulations to study the coupling between
morphology, kinematics and metallicity of the bar/bulge region of our Galaxy.
We make qualitative comparisons of our results with available observations and
find very good agreement. We conclude that this region is complex, since it
comprises several stellar components with different properties -- i.e. a
boxy/peanut bulge, thin and thick disc components, and, to lesser extents, a
disky pseudobulge, a stellar halo and a small classical bulge -- all cohabiting
in dynamical equilibrium. Our models show strong links between kinematics and
metallicity, or morphology and metallicity, as already suggested by a number of
recent observations. We discuss and explain these links.Comment: 5 pages, 4 figures, accepted for publication in MNRAS Letter
Forming disc galaxies in major mergers: III. The effect of angular momentum on the radial density profiles of disc galaxies
We study the effect of angular momentum on the surface density profiles of
disc galaxies, using high resolution simulations of major mergers whose
remnants have downbending radial density profiles (type II). As described in
the previous papers of this series, in this scenario, most of the disc mass is
acquired after the collision via accretion from a hot gaseous halo. We find
that the inner and outer disc scalelengths, as well as the break radius,
correlate with the total angular momentum of the initial merging system, and
are larger for high angular momentum systems. We follow the angular momentum
redistribution in our simulated galaxies, and find that, like the mass, the
disc angular momentum is acquired via accretion, i.e. to the detriment of the
gaseous halo. Furthermore, high angular momentum systems give more angular
momentum to their discs, which affects directly their radial density profile.
Adding simulations of isolated galaxies to our sample, we find that the
correlations are valid also for disc galaxies evolved in isolation. We show
that the outer part of the disc at the end of the simulation is populated
mainly by inside-out stellar migration, and that in galaxies with higher
angular momentum, stars travel radially further out. This, however, does not
mean that outer disc stars (in type II discs) were mostly born in the inner
disc. Indeed, generally the break radius increases over time, and not taking
this into account leads to overestimating the number of stars born in the inner
disc.Comment: 12 pages, 13 figures, accepted for publication in MNRA
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