SIMBAD references

The phase space, as coded by kinematic parameters and chemical abundances, is crucial for understanding the formation of the Galactic disk. Using red giant stars from the Galactic thin disk with [Fe/H] > - 0.8 and low-α ratios identified in LAMOST-Gaia, we detect numerous ridges and undulations in the R-V_ϕ diagram coded by median V_R. Strikingly, the slope of these features changes from -22 km s^–1 kpc^–1 to -8 km s^–1 kpc^–1 at R ∼ 11.5 kpc. Accordingly, the R_g-V_ϕ plane, also coded by median V_R, reveals wave-like structures that propagate outwards in the inner disk but reverse direction and move inwards beyond R_g = 11.5 kpc. The most prominent feature is the G1 group, distinguished by its wider spread and negative median V_R at R_g∼ 15 kpc, contrasting with the narrower G0 group that exhibits positive median V_R at R_g < 11.5 kpc. Furthermore, the [C/N] versus [Fe/H] relationship for the G1 group mirrors the opposite trend compared to the G0 group. Since [C/N] serves as a proxy for age, this contrasting behavior suggests an inverse age-metallicity relation for the G1 group. Comparison with the Sagittarius dwarf galaxy reveals that the G1 group possesses distinct [Mg/Fe] and [Al/Fe] ratios, yet its [C/N] versus [Fe/H] pattern is similar to that of the Sgr dwarf galaxy. Based on these observations, we proposed that the inward-moving and asymmetric velocity wave G1 might be linked to the minor merge of the Sagittarius galaxy.