The outer Galaxy provides a unique opportunity to study the impact of metallicity on star formation at a spatial resolution sufficient to resolve individual clumps and cores. The metallicity declines as a function of Galactocentric radius and is in between that of the Magellanic Clouds and the inner Galactic disk. The reduced abundances of dust and molecules heavier than H2 affect the overall gas and dust cooling budget. The average flux of cosmic rays and the ultraviolet radiation field strengths are lower, but both high energy particles and radiation penetrate deeper into the clouds due to less shielding. The differences in environmental conditions and the high fraction of atomic-to-molecular gas are expected to lower the star formation rate per surface area. Together with the well studied, higher-metallicity local molecular clouds, the clouds in the outer Milky Way offer a unique opportunity to study the impact of metallicity on star formation.
In this talk, I will review recent observational efforts in the outer Galaxy from physical scales from clouds to cores. On cloud scales, I will present research highlights from the APEX 'Outer Galaxy High Resolution Survey' (OGHReS), probing CO emission in the entire 3rd quadrant of the Galaxy with unprecedented detail, and from complementary surveys using denser gas tracers (e.g. HCN, HCO+) and atomic carbon. Next, I will discuss the gradients of molecular abundances in star-forming clumps across the Galactic disk, indicating the underlying role of metallicity. On core scales, I will discuss studies of outflow activity in the outer Galaxy using JWST and ALMA/NOEMA. I will conclude with emphasizing key differences between the outer Galaxy with the Solar neighborhood, and links with extragalactic star formation.
