Striations, wisps and arcs - the fascinating evolution of filaments in a violent environment

• Applicant: Professor Dr. Andreas Burkert
• Subject Area: Astrophysics and Astronomy
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 263084359

The multi-phase interstellar medium (ISM) consists of a complex network of dense and cold filamentary structures that are embedded in a diffuse, hotter medium. The filaments are believed to form by compressional, converging flows as a result of interstellar turbulence, by large scale spiral arms or by gravitational disk instabilities. It is generally believed that they are destroyed as soon as they condense into stars which disperse their environment by their ionizing radiation and stellar winds. Up until now, filaments have often been treated as isolated, homogeneous structures. However, recent observations indicate that filaments are much more complex than assumed so far. Irregular internal velocity fields have been detected indicating that filaments are actually bundles of narrow, interacting strings. In addition, new recent observations show that filaments are often embedded in large-scale gas flows that strongly affect their evolution. These flows result from nearby star-forming regions that generate violent outflows, ejecting low-density warm and hot gas into the galactic environment. We propose to investigate the interaction of dense gas filaments with surrounding winds, generated by nearby star-forming regions. We want to explore how the internal density field and turbulent velocity structure of a filament is affected by its interaction with the wind that leads to hydrodynamical instabilities (e.g. Kelvin-Helmholtz) in the interaction zone and drives density waves into the inner filamentary region. These interactions may explain the complex velocity structure observed. In addition, it can trigger star formation but also could destroy segments of a filament prior to star formation by mixing cold and dense filamentary gas with the diffuse, hotter wind material. As an excellent test case, we will focus on the fascinating substructures detected recently in the filament Barnard 44 (Ophiuchus) by Alves et al. Our results will provide important information on the evolution of filaments that are the fundamental building blocks of molecular clouds, especially on their intimate coupling with their turbulent and violent surrounding.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1573: Physics of the Interstellar Medium