Observing Chaos in Disk Galaxies

Abstract

Regions in disk galaxies where one would expect to find chaotic behavior are likely to be associated with major stellar resonances such as the co-rotation. The possible identification of such locations in real galaxies is illustrated by examples of four spiral galaxies observed in the K band. Observational issues related to the detection of chaotic regions are discussed. Although surface photometry may suggest chaotic regions, it is essential to compare detailed velocity profiles with dynamic models to estimate the probability of such claims. Finally, the feasibility of performing observations of chaos with current state-of-the-art facilities such as the VLT is considered. It is found that it should be possible down to a surface brightness level of I ≈ 20 mag/arcsec² corresponding to the end of bars in typical disk galaxies whereas access to detailed studies of chaos in the main spiral pattern would require more powerful facilities.

Based on observations collected at the European Southern Observatory, La Silla, Chile.