Matter ghost matter astrophysics.6:
Spiral structure.(p7)
- Results.
-
After two turns (figure 13-a):
The first irregularities appears at the frontier between cluster and halo.
This effect comes from short distance interactions between the two populations.
This may be understood by a dynamic friction. This first tiny arms already
show some curvature. -
Four turns (figure 13-b):
The dynamic friction is at its maximum. The speed of cluster masses at the
frontier increases. This tends to dissipate the first structures. There is
a energy transfer between the two population. The Jeans conditions of the
halo changes. The halo shows its first irregularities. -
Four turns and half (figure
13-c) : The halo irregularities are now more contrasted. The effects of the
dynamic friction have now completely disappeared. The first structures are
now surrounding the kernel. This set of positive masses will build the future
arms, influenced by the tidal effects from the four clusters of the halo. -
Eight turns (figure 13-d)
: The tidal effect curves the belt of positive particles surrounding the
kernel. Four arms clearly appear. -
Ten turns (figure 13-e) : The
tidal effect has melted two arms together. This structure is the first stable
spiral shape which will last till the end of the simulation -
Twelve turns (figure 13-f) :
The spiral structure is now well contrasted. As the halo is now larger because
of the rotation of the cluster, the dynamical friction becomes nglectible
and the tidal effect runs the process, inducing a slow beaking to the cluster.
This spiral structure will last over fifty turns.
We tried to choose the most relevant
run as an illustration. This scenario of the birth of a galaxy is, to some
extend, the same for all our simulations. The dynamic effects are of course
much more evident with an animation. This was a great help for us as we do
not have a mathematical model for a cluster in rotation (the 2-d Eddington
corresponds to a non-rotating population of particles). Within six months
we reached a set of parameters which create these spiral effects structure.
These parameters seem to have precise value. Changing them drastically, and
the galactic structure becomes unstable.
.
Fig. 13 a
: The galaxy with its surronding anti galaxy.
Two turns. Dynamical friction
dominating.
.
.
Fig. 13 b: The galaxy with its surronding anti galaxy.
Four turns. Idem
.
Fig. 13 c : The galaxy with its surronding
anti galaxy.
Four turns and half. The small
arms have disappeared.
