Periodic Reporting for period 1 - BEYONDCO (Using fine structure line emission to observe the life-cycle of molecular clouds)
Reporting period: 2016-10-06 to 2018-10-05
There is a growing consensus within the international community that fine structure line (FSL) tracers -- specifically ionised and atomic carbon ([CII] and [CI]) and atomic oxygen ([OI]) -- are the key probes of the earliest stages of cloud assembly, as they are chemically abundant in regions surrounding MCs where CO is not. As such, FSLs are able to trace the low-density transition from atomic to molecular gas that marks the boundary from the warm ISM to the cold reservoirs in which stars form. They also constitute the main coolants of ISM during this transition, thus providing a way to measure the energetics of the ISM. It is only within the last few years that we have gained the technological capabilities to map FSL emission in and around Galactic star formation sites. First with the Herschel Space Observatory and now with the Stratospheric Observatory for Infrared Astronomy (SOFIA), [CII] and [OI] mapping are possible. The Atacama Pathfinder Experiment (APEX) telescope can also map [CI] emission. With these facilities, it is now possible to measure the mass and dynamics of the “CO-dark” molecular and cold atomic gas that surround and permeate MCs, and combine this with our extensive knowledge of CO-traced cloud and the star formation inventory within.
The main objective of this project was to use FSL tracers alongside more traditional MC tracers to gain a broader understanding of the connection between MCs and their environment. We did this by examining the morphology and dynamics of a sample of clouds and comparing those results to numerical simulations, which helped us to identify the important physical mechanisms in the cloud formation.