Oral Presentation

ALMA View of Chemistry of Hot Molecular Cores at Low Metallicity

Author(s): Takashi Shimonishi (Niigata Univ.)

Presenter: Takashi Shimonishi (Niigata University)

Understanding chemistry of interstellar medium at low metallicity is crucial to unveil chemical processes in high-redshift galaxies and the past Galactic environment, where the metallicity was significantly lower compared to the present-day solar neighborhood. Hot molecular cores are one of the early stages of star formation and they play a key role in the chemical processing of interstellar molecules, especially for complex species. Chemistry of hot cores at low metallicity is now emerging with discoveries of hot cores with ALMA in a nearby low-metallicity galaxy, the Large Magellanic Cloud (LMC) (Shimonishi et al. 2016; Sewilo et al. 2018).
Here I will present the latest ALMA data on a newly-discovered hot molecular core in the LMC, which provide us with the unprecedented amount of molecular line data on the chemical complexity of star-forming regions at low metallicity (Shimonishi et al. 2019 in prep.). A comparison of molecular abundances between LMC and Galactic hot cores suggests that organic molecules (e.g., CH3OH, a classical hot core tracer) show a large abundance variation in low-metallicity hot cores. There are organic-poor hot cores that are unique in the LMC, while there are relatively organic-rich hot cores, whose abundances of organic molecules roughly scale with the metallicity. Our astrochemical simulations suggest that different grain temperature during the initial ice-forming stage would contribute to the chemical variety. On the other hand, particular molecules such as SO2 show relatively constant and metallicity-scaled abundances within known LMC hot cores. The above results suggest that molecular abundances in star-forming regions do not always simply scale with the elemental abundances of the parent galaxy. In this presentation, I will summarize the current status and scientific outcomes of hot core observations towards low-metallicity systems with ALMA, and discuss chemical characteristics of star-forming regions at low metallicity.