The Resonant Structure of Galaxy Disks
John Beckman (Instituto de Astrofísica de Canarias)

Disk galaxies such as the Milky Way represent more than half of the population of galaxies in the local universe. Among their most recognizable properties are their spiral arms and some two thirds of them have characteristic barred concentrations of their stellar populations. It is now classical astrophysics that the presence of stable long-lived arms can only be explained by the presence of a spiral density wave in the disk, strongly stimulated by the bar. But theorists showed, around the turn of the millenium, that they could use the angular rotation speed of the bars in local galaxies to determine the predicted braking effect of dark matter halos on them, and when they did this they found that bars in general are rotating too fast. No evidence of the dark matter braking. Was there a basic flaw in the CDM cosmological scenario? In the talk I will explain how, in my group, we aimed to verify this, using a new technique to relate the internal kinematics of bars and arms to the dynamics of the rotating galaxies. We found a compex, but surprisingly elegant resonant structure in disks, and resolved the problem of the bars spinning too quickly. I will end by showing how our technique has probed the history of the dynamical interaction of M51 with its satellite galaxy NGC 5195.

TBD
Cole Miller (UMD)

TBD
Spencer Hulsey (UIUC)