Environmental Engineering Reference
In-Depth Information
=
.
.
.
encounters, for
p
05 Gyr,
respectively. Increasing impact parameter increases the times of the first and second
encounters. For all the numerical experiments we look for a bar formation in each
of the galaxies for times between the first and second encounter and we analyse the
morphology of these bars at times chosen uniformly in that time interval.
Figure
3
shows snapshots of the collisions for the three values of the impact
parameter and a collision angle of 30
ⓦ
. Morphology of galaxy 2 for a 0
ⓦ
angle of
collision is similar as the one of galaxy 1. Galaxy 2 for a collision angle different
from 0
ⓦ
turns to warped disc shape, this is due to that galaxy 1 collides with it
crossing its disc very dramatically, but, in spite of this, the bar is formed as it is
shown in Fig.
4
. The disc of galaxy 1 does not change its shape because it collides
like a knife. In this figure we show the morphology of the bars formed in galaxy 1 and
galaxy 2, i.e., the sizes of minor and major axes as function of time found with the
method we described above. Morphology of the bar is almost the same for
p
0
1, are, approximately, at time 0
38 Gyr and at 1
=
0
.
3
and
p
=
0
.
6. For
p
=
0
.
1 the major (minor) axis is longer (smaller) than the ones
for
p
6. Whereas changing the angle between disc planes does not
change morphology for
p
=
0
.
3 and
p
=
0
.
=
0
.
1.
4 Conclusions
Our simulations have shown that tidal forces are an efficient mechanism to generate
bars in spirals. In all our numerical experiments a bar is formed in both colliding
galaxies after the first encounter. The morphology of the barred spirals that result
from the collision does not show strong dependence on the geometry of the collision
for galaxies like “galaxy 1” that is colliding like a knife. Whereas galaxies like
“galaxy 2” show a decreasing, in time, major axis size for small impact parameters.
This behaviour could be due to the fact that disc of galaxy 2, after first encounter
acquires a warped shape.
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