Hydroxyl as a Probe of the Interstellar Medium

Wednesday 10 Aug 2022 @ 12:00 p.m., Zoom
Dr Anita Petzler, CSIRO; Email: Anita.Petzler[at]csiro.au


The molecular gas of the interstellar medium provides the raw material for star formation, yet its principle component – molecular hydrogen – is essentially invisible at radio wavelengths. Instead we must infer its presence and properties through the study of other tracer molecules, such as hydroxyl (OH). OH, with its four ground-rotational transitions at 1612, 1665, 1667 and 1720 MHz is a challenging molecule to observe due both to the weakness of its lines and the complexity of their excitation. However, the complex excitation of OH holds valuable information about the host molecular gas. The satellite lines at 1612 and 1720 MHz in particular, with their ubiquitous anomalous excitation, are much more sensitive to local conditions than the main lines which rarely diverge from their expected excitation at local thermodynamic equilibrium (LTE). In this talk I will discuss my PhD research which focused on exploring the utility of this interesting molecule. I will also introduce my current project which is to monitor the time-variability of high-gain OH masers in star forming regions.