Distribution of the targets observed in this work across the Milky Way in white ‘+’ symbols along with their identifiers, as listed in Table 1. The red asterisk and Sun symbols mark the Galactic centre at (0, 0) kpc and the position of the Solar System at (0, −8.15) kpc, respectively (Reid et al. 2019000000). The sources are projected onto the Galactic plane with parallax-based distances from Reid et al. (2019). The underlying Milky Way spiral arm pattern follows the log-periodic model from the same study, with colours adapted from Jacob et al. (2022). The background image is an artist’s impression of the large-scale structure of the Milky Way, courtesy of ESA/Gaia/DPAC/Stefan Payne-Wardenaar.