spiral structure Ghost matter astrophysics.6: Spiral structure. (p7)
- Results. - After two turns (figure 13-a): The first irregularities appear at the boundary between the cluster and the halo. This effect arises from short-range interactions between the two populations. It can be understood through dynamical friction. These initial small arms already exhibit some curvature.
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Four turns (figure 13-b): Dynamical friction reaches its peak. The velocity of cluster masses at the boundary increases. This tends to dissipate the earliest structures. Energy is transferred between the two populations. The Jeans conditions of the halo change. The halo displays its first irregularities.
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Four and a half turns (figure 13-c): The halo's irregularities are now more pronounced. The effects of dynamical friction have completely vanished. The first structures now encircle the core. This group of positive masses will form the future arms, influenced by tidal effects from the four clusters within the halo.
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Eight turns (figure 13-d): The tidal effect bends the belt of positive particles surrounding the core. Four distinct arms clearly emerge.
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Ten turns (figure 13-e): The tidal effect has merged two arms into one. This structure represents the first stable spiral form, which will persist until the end of the simulation.
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Twelve turns (figure 13-f): The spiral structure is now well defined. As the halo has grown larger due to cluster rotation, dynamical friction becomes negligible, and tidal effects dominate the process, causing a slow deformation of the cluster. This spiral structure will endure for over fifty turns.
We attempted to select the most relevant simulation as an illustration. This scenario of galaxy formation is, to some extent, consistent across all our simulations. Dynamic effects are, of course, much more apparent in animation. This proved invaluable, as we lack a mathematical model for a rotating cluster (the 2D Eddington model applies to a non-rotating population of particles). Within less than six months, we identified a set of parameters capable of producing these spiral structures. These parameters appear to have precise values; significantly altering them causes the galactic structure to become unstable.
. Fig. 13 a : The galaxy with its surrounding anti-galaxy. Two turns. Dynamical friction dominant.**** . . Fig. 13 b: The galaxy with its surrounding anti-galaxy. Four turns. Same as above **** . Fig. 13 c : The galaxy with its surrounding anti-galaxy. Four turns and a half. The small arms have disappeared. 