Constrain the functional form of the metal-poor Splash component

Determine the intrinsic functional form of the older, metal-poor component in the Splash population’s joint age–metallicity distribution, distinguishing between the preferred two-Gaussian description and alternative forms such as a Gaussian plus a truncated power-law component.

Background

The forward modeling of Splash stars with [Fe/H] > −1 robustly identifies two components: a broad, relatively younger and more metal-rich component and a concentrated, older and more metal-poor component. The two-Gaussian model is preferred by the information criteria and marginal goodness-of-fit tests.

However, the data also admit a Gaussian-plus-power-law description that recovers a similar concentrated metal-poor component. The precise distributional form of this component is therefore unresolved, even though the existence of an intrinsic two-component structure is considered robust.

References

Thus, although the precise functional form of the metal-poor component is not uniquely constrained, the presence of an intrinsic two-component structure in the age--[Fe/H] distribution is robust.

— The Milky Way's Early Disk Was Built in Bursts. I. Evidence from Low-angular-momentum, High-$α$ Stars Scattered Out of the Protodisk by Merger Events  (2610.26374 - Sun et al., 19 Oct 2026) in Section 5, “Conclusions”