The Role of GMC Observations in the Big Picture
Hokkaido U, Sapporo, JP
Observations with ALMA are about to resolve a wide population of giant molecular clouds (GMCs). This is immensely helpful for understanding star formation, since the cloud properties set the conditions for new star birth.
However, while more structures and phases of the GMCs will be resolved, it is necessary to rethink what are we really looking at through the telescope. What is the underlying origin of the observed properties of GMCs, such as the measured quantities of mass, size, velocity dispersion, and their further implications, such as the Larson's scaling relations. Moreover, since observational bias, e.g., projection effects, galactic disc inclinations, finite resolution and sensitivity, are unavoidable, what can (and cannot) observations tell us about GMCs and the galaxy's molecular gas? Finally, if the environmental dependancies on GMCs properties which is believed to be in charge of the varying star formation efficiency among Galactic regions and galaxies do exist, are we yet at the stage where we can detect this through observations?
In this research, we compare the physical properties of the GMCs identified in high-resolution simulated galaxies in position-position-position space (PPP) and those in observational position-position-velocity space (PPV) in the same simulated galaxies. The synthetic observations are carried out using the ALMA simulator in CASA, assuming various galaxy inclinations, observed resolutions, and sensitivities. The simulations include different types of galactic environments, allowing us to test the above three questions. Our main results suggest that the observed GMC properties and the Larson's scaling relations are not entirely driven by the underlying physical origin and therefore have to be used with caution. The environmental dependence of GMCs can be distinguished only when the observational biases are known.
E.J. Tasker, Hokkaido U, JP
Y. Fujimoto, Hokkaido U, JP
E. Rosolowsky, U Alberta, CA
D. Colombo, U Alberta, CA
S.M. Benincasa, McMaster U, CA
J. Wadsley, McMaster U, CA
Suggested Session: Molecular Clouds