The Formation of Giant Molecular Clouds and their Associations: Confronting Theory with Observations in Spiral Arms

• Applicant: Dr. Eva Schinnerer
• Subject Area: Astrophysics and Astronomy
• Term: from 2011 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 203331805

Galactic spiral arms have long been suspected to govern the formation of Giant Molecular Clouds (GMCs) and subsequent star formation, however, observations and theory remain inconclusive and contradictory. Results from our 40pc resolution molecular gas survey PAWS (PdBI Arcsecond Whirlpool Survey) obtained during the first ISM-SPP funding period show that molecular gas and star formation do not always trace each other, and molecular gas properties and, especially, those of GMCs exhibit a strong dependence on galactic environment (nucleus, arm, inter-arm) -- fully unexpected from current models. This immediately implies that different regimes of GMC and thus star formation exist in spiral disk and that other factors, such as, e.g. dynamical pressure might play an important role. Therefore funding is requested to exploit two new exquisite datasets from ALMA and the Jansky VLA to further investigate the formation of molecular clouds and stars in the presence of spiral arms. Sensitive ALMA observations (5sigma ~ 2e4 M_sun mass limit) of the central 7.5 kpc in the nearby grand-design spiral galaxy NGC628 will be used to investigate the hierarchical structure of the molecular gas and its dependance on galactic environment in unprecedented detail. This investigation is crucial to confirm the unexpected PAWS results. The PAWS M51 molecular gas data will be combined with similar resolution imaging of the thermal radio continuum (regarded a 'gold standard' as star formation rate tracer) to test several theories proposed for star formation 'laws'. The requested post-doc and PhD researcher will work on the first and second project, respectively.

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