The Milky Way’s enrichment across five nucleosynthetic channels from 4 million LAMOST spectra

This represents our efforts to derive detailed abundances from LAMOST spectra using the cannon. We used GALAH as a source of training data, and we obtained access to the GALAH spectra in order to make chi^2 cuts on our training set different from those flagged in the GALAH dr2 catalog. A pdf of our latest draft (nearly ready for submission) is attached. Apologies for not circulating it sooner.

abstract: Large stellar surveys are revealing the chemodynamical structure of the Galaxy across a vast spatial extent. However, the many millions of low-resolution spectra observed to date have only been partially exploited. We employ \thecannon, a data-driven approach to calculating abundances, to derive up to seven individual element abundances from low-resolution (R = 1800) LAMOST spectra. We deliver measurements of up to six of [O/Fe], [Eu/Fe], [$\alpha$/Fe], [Sc/Fe], [s-process/Fe], [Mg/Fe], [Al/Fe], [Mn/Fe], and [Ba/Fe], which represent five different nucleosynthetic channels, for 3.9 million stars, to a precision of 0.06 - 0.24 dex. We demonstrate the additional discriminating power beyond bulk metallicity that is provided by these elements by analyzing the abundances of co-moving pairs and wide binaries. We investigate the flaring of the disk seen in the abundances, presumably as a consequence of radial migration, explore azimuthal abundance trends across the disk, and show the disk-halo transition in the neutron-capture abundances. LAMOST has near-complete Gaia coverage, which provides an unprecedented perspective on chemodynamical evolution.