Radial Migration in Disk Galaxies I: Transient Spiral Structure and Dynamics

TL;DR

This paper investigates how transient spiral structures in idealized galactic disks cause radial migration of stars, emphasizing the role of resonant scattering at corotation points and confirming the Sellwood & Binney mechanism.

Contribution

It demonstrates that multiple transient spiral patterns coexist and influence stellar orbits, with the corotation scattering mechanism being the primary driver of angular momentum changes.

Findings

Multiple transient spiral patterns are common in isolated disks.

Resonant scattering at corotation significantly alters stellar angular momentum.

Spiral properties are robust across different numerical resolutions.

Abstract

We seek to understand the origin of radial migration in spiral galaxies by analyzing in detail the structure and evolution of an idealized, isolated galactic disk. To understand the redistribution of stars, we characterize the time-evolution of properties of spirals that spontaneously form in the disk. Our models unambiguously show that in such disks, single spirals are unlikely, but that a number of transient patterns may coexist in the disk. However, we also show that while spirals are transient in amplitude, at any given time the disk favors patterns of certain pattern speeds. Using several runs with different numerical parameters we show that the properties of spirals that occur spontaneously in the disk do not sensitively depend on resolution. The existence of multiple transient patterns has large implications for the orbits of stars in the disk, and we therefore examine the resonant scattering mechanisms that profoundly alter angular momenta of individual stars. We confirm that the corotation scattering mechanism described by Sellwood & Binney (2002) is responsible for the largest angular momentum changes in our simulations.