Another field to which Dr Johnston has made a significant contribution is the study of molecular cloud properties and the formation of stars in the extreme environment towards the Galactic Centre. The most prominent example is her work on the Galactic centre cloud G0.253+0.016 based on SMA observations (Johnston et al. 2014). One of the main findings of this work was that there is no fixed surface density threshold for star formation, but instead that the level of turbulence and background density in a region must be first accounted for. Alongside this work, she collaborated on several other projects investigating the enigmatic environment of the Central Molecular Zone (e.g. Kendrew et al. 2013, Bally et al. 2014, Koepferl et al. 2015, Walker et al. 2018). In addition to using long-wavelength (>IR) observations to decipher the structure and properties of molecular clouds in the Galactic Centre, she has contributed to several works investigating filaments at different size-scales in the Galaxy and their role in star formation (Kainulainen et al. 2017, Abreu-Vicente et al. 2016, Beuther et al. 2015, Ragan et al. 2014). Dr Johnston was also one of the leading team members of the THOR collaboration, a VLA 1.4GHz Galactic Plane survey to study the path of cloud formation from HI to molecular gas (Beuther et al. 2016, Walsh et al., 2016, Bihr et al. 2015, 2016, Wang et al. 2018, 2020).
