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We have analysed the chemical and kinematic properties of the 20 and 50 km s$^{-1}$ molecular clouds in the Central Molecular Zone of the Milky Way Galaxy, as well as those of the molecular ridge bridging these two clouds. Our work has utilized 37 molecular transitions in the 0.65, 3 and 7-mm wavebands, from the Mopra and NANTEN2 telescopes. The 0.65-mm NANTEN2 data highlights a dense condensation of emission within the western part of the 20 km s$^{-1}$ cloud, visible in only four other transitions, which are 3-mm H$^{13}$CN (1--0), H$^{13}$CO$^{+}$ (1--0), HNC (1--0) and N$_{2}$H$^{+}$ (1--0), suggesting that the condensation is moderately optically thick and cold. We find that while the relative chemical abundances between both clouds are alike in many transitions, suggesting little variation in the chemistry between both clouds; the 20 km s$^{-1}$, cold cloud is brighter than the 50 km s$^{-1}$ cloud in shock and high density tracers. The spatial distribution of enhanced emission is widespread in the 20 km s$^{-1}$ cloud, as shown via line ratio maps. The position velocity diagrams across both clouds indicate that the gas is well mixed. We show that the molecular ridge is most likely part of the 20 km s$^{-1}$ cloud and that both of them may possibly extend to include the 50 km s$^{-1}$ cloud, as part of one larger cloud. Furthermore, we expect that the 20 km s$^{-1}$ cloud is being tidally sheared as a result of the gravitational potential from Sgr A*.
The evolution of molecular clouds in galactic centres is thought to differ from that in galactic discs due to a significant influence of the external gravitational potential. We present a set of numerical simulations of molecular clouds orbiting on t
We present Keck/DEIMOS spectroscopy of individual stars in the relatively isolated Local Group dwarf galaxies Leo A, Aquarius, and the Sagittarius dwarf irregular galaxy. The three galaxies--but especially Leo A and Aquarius--share in common delayed
We have investigated the role of molecular anion chemistry in pseudo-time dependent chemical models of dark clouds. With oxygen-rich elemental abundances, the addition of anions results in a slight improvement in the overall agreement between model r
Astrochemistry lies at the nexus of astronomy, chemistry, and molecular physics. On the basis of precise laboratory data, a rich collection of more than 200 familiar and exotic molecules have been identified in the interstellar medium, the vast major
We present a general parameter study, in which the abundance of interstellar argonium (ArH$^+$) is predicted using a model for the physics and chemistry of diffuse interstellar gas clouds. Results have been obtained as a function of UV radiation fiel