http://arxiv.org/abs/2109.00458
The formation and disappearance of spiral arms are studied by focusing on jammed Keplerian gas in a coupled map lattice (CML) with a minimal set of procedures for simulating diverse patterns in astronomical objects. The CML shows that a spiral arm is a type of traffic jam, and its motion is governed by both a gas inflow into and outflow from the jam. In particular, a new mechanism for the disappearance of spiral arms is found. It is caused not by conventional differential rotation, but by the gas flow rate difference between the light inflow and heavy outflow, here called “light-in and heavy-out”, leading to the disappearance of traffic jams. Furthermore, we propose a general approximate formula for the lifetime of spiral arms, which is simply derived from the mechanism of the “light-in and heavy-out”. The proposed formula is successfully applied to the CML simulations, and moreover, to the observational data of the spiral galaxy M51.
E. Nozawa
Thu, 2 Sep 21
43/59
Comments: 8 pages, 4 figures