COLLOQUIUM: Daniel Seifried, Universität Köln

Magnetic fields in molecular clouds - Impact on the dynamics and chemistry

I present results of fully self-consistent synthetic dust polarisation maps of simulated molecular clouds (MCs) created with POLARIS (Seifried et al., 2019+2020a). The MCs form in simulations of a 3-phase ISM which include its detailed chemical and dynamical evolution.  By incorporating noise in our synthetic maps, we assess the reliability of polarisation observations from e.g. Planck and BlastPol. I will discuss how projection effects affect the observed orientation of magnetic fields. Furthermore, I will show that polarisation observations of MCs mainly probe their dense parts up to AV > 1 (~1000 cm^-3). In addition, I combine the results with analytical considerations to shed light on the dynamical importance of magnetic fields. I will show that magnetic fields become perpendicular to (column) density structures above N = 10^(21-22) cm^-2 and n ~ 1000 cm^-3 and discuss how this orientation flip relates to the question where and when gravity starts to dominate over magnetic fields  . In order to complete the picture, I will finally briefly shed light on how magnetic fields influence the chemical evolution of molecular clouds by making their structure more fluffy and diffuse (Seifried et al., 2020b) as this has a direct impact on both the amount of H2 and CO-dark gas. In addition, I will discuss how the switch of the magnetic field orientation is related to the chemical state of the gas. This will allow us to gain a more complete view on how magnetic fields affect both the dynamics and chemical evolution of molecular clouds

Talk in presence and via Zoom:

https://uni-hamburg.zoom.us/j/66006535328?pwd=aGkrSjJIYmZjK0VpYlpGL0ZrdHg2UT09

Meeting ID: 660 0653 5328

Passcode: 20658852