The life-cycle of turbulent molecular clouds

• Applicants: Professor Simon Glover, Ph.D.; Professor Ralf Klessen, Ph.D.; Dr. Thorsten Naab; Professorin Dr. Stefanie Walch-Gassner
• Subject Area: Astrophysics and Astronomy
• Term: from 2014 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 263083489

A full understanding of the multi-phase structure of the turbulent interstellar medium (ISM) is one of the single most important challenges in modern astrophysics. The complex interplay and relative contributions of gravitational collapse, radiative cooling, the formation and destruction of molecules, the impact of ionising radiation, stellar winds, supernova explosions from massive stars, and the role of magnetic fields is still poorly understood. It can only be investigated in detail with challenging high-performance numerical simulations. Triggered by the establishment of the ISM SPP1573 about three years ago, a group of SPP members (the PIs of this proposal) have joined their expertise to investigate the multi-phase ISM by means of numerical simulations with an unprecedented combination of resolution and physical complexity. Supported by a major grant of computational time (42 million CPU hours at SuperMUC) we have developed and tested a massively parallel version of the magneto-hydrodynamic, adaptive mesh refinement grid code FLASH including self-gravity, chemistry, and radiative transfer for point sources and diffuse radiation fields. With this unique tool, we will simulate the full life-cycle of molecular clouds in the ISM in different environments, from their assembly through to their destruction by stellar feedback and the launching of multi-phase galactic winds. We will also post-process our simulations to generate synthetic line emission maps and dust continuum images that we will compare in detail with data from state-of-the-art observational surveys, including some for which we have privileged access. This will allow us to self-consistently address key science questions with unprecedented precision and predictive power: How do molecular clouds form and how are they dispersed by massive stars in galactic discs of varying surface density? What is the respective role of ionising radiation, stellar winds and supernova explosions in this context? How is turbulence generated in the molecular, neutral and ionised phases of the ISM? How can the feedback from massive stars drive highly turbulent motions and multi-phase ISM galactic winds and outflows, which appear to be the main regulator for galaxy formation? What is the role of magnetic fields? How can we construct accurate synthetic observations from our simulations? How can novel observations of the ISM in the disc and in galactic outflows (e.g. molecular lines) be interpreted theoretically? Can we make definite scientific predictions for existing and upcoming observations (e.g. ALMA) of the galactic ISM across cosmic time? After finishing the initial phase of method development, we can now harvest on our investments and apply the capabilities developed in the past years to address all the above questions in a major joint effort, for which we ask for the support within the SPP.

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