Quantitative chemical tagging: empirical constraints on the identification of dispersed coeval stellar groups

Though it has been established that open clusters have tight abundance scatter, the empirical evidence for the viability of chemical tagging has for the most part gone unstudied. With a large survey dedicated to tagging - GALAH - just on the horizon, we perform several empirical investigations of this technique. An empirical coeval probability function, which quantifies the likelihood that a pair of stars originated from the same star formation event, is developed and characterised. We then perform a real world test by conducting the first ever blind chemical tagging experiment, with several important implications. The long term evolution and the origin of the Galactic stellar disc are the subjects of intense study. Much is surmised about the evolution of galaxies in general by studying those at cosmic scales, yet there are still significant issues in explaining phenomena in our own Galaxy. It is only a single case, but of universal importance due to our ability to resolve individual stars and stellar populations. Amongst the important open questions are the origin (or indeed the reality) of the thin and thick stellar discs, the role of intra-disc stellar migrations, the merger history, in-situ star formation history and the chemical evolution of the disc. Kinematic information, though crucial to understanding the Galactic environment, is short lived in the disc and thus astronomers are turning to stellar chemical abundances, which remain unchanged for most of a star's lifetime, to reveal history. In particular, the technique of chemical tagging may be able to use this "fossil" information to link groups of stars in the disc which have formed concurrently from the same molecular cloud, but have since dispersed. Though it has been established that open clusters have tight abundance scatter, the empirical evidence for the viability of chemical tagging has for the most part gone unstudied. With a large survey dedicated to tagging - GALAH - just on the horizon, we perform several empirical investigations of this technique. An empirical coeval probability function, which quantifies the likelihood that a pair of stars originated from the same star formation event, is developed and characterised. We then perform a real world test by conducting the first ever blind chemical tagging experiment, with several important implications.