The abundance ratios of manganese to iron in late-type stars across a wide metallicity range place tight constraints on the astrophysical production sites of Fe-group elements .
In this work , we investigate the chemical evolution of Mn in the Milky Way galaxy using high-resolution spectroscopic observations of stars in the Galactic disc and halo stars , as well as a sample of globular clusters .
Our analysis shows that local thermodynamic equilibrium ( LTE ) leads to a strong imbalance in the ionisation equilibrium of Mn I and Mn II lines .
Mn I produces systematically ( up to 0.6 dex ) lower abundances compared to the Mn II lines .
Non-local thermodynamic equilibrium ( NLTE ) radiative transfer satisfies the ionisation equilibrium across the entire metallicity range , -3 \lesssim [ Fe / H ] \lesssim - 1 , leading to consistent abundances from both ionisation stages of the element .
We compare the NLTE abundances with Galactic Chemical Evolution models computed using different sources of type Ia and type II supernova ( SN Ia and SN II ) yields .
We find that a good fit to our observations can be obtained by assuming that a significant ( { \sim } 75 \% ) fraction of SNe Ia stem from a sub-Chandrasekhar ( sub- M _ { ch } ) channel .
While this fraction is larger than that found in earlier studies ( { \sim } 50 \% ) , we note that we still require { \sim } 25 \% near- M _ { ch } SNe Ia to obtain solar [ Mn/Fe ] at [ Fe/H ] = 0 .
Our new data also suggest higher SN II Mn yields at low metallicity than typically assumed in the literature .