Evidence for Co-rotation Origin of Super Metal Rich Stars in LAMOST-Gaia: Multiple Ridges with a Similar Slope in phi versus Lz Plane

TL;DR

This study provides evidence that super metal-rich stars in the solar neighborhood likely originate from the inner disk through co-rotation resonance with the Galactic bar, supported by observed ridges and undulations in phi versus Lz space.

Contribution

It presents observational evidence linking super metal-rich stars to the co-rotation resonance of the Galactic bar, including the detection of specific ridges and undulations in phase space.

Findings

Detected six ridges and undulations in phi versus Lz space.

Observed a slope of approximately -8 km/s kpc/deg consistent with models.

Indications of minor merger effects from Sagittarius dwarf galaxy.

Abstract

Super metal-rich (SMR) stars in the solar neighborhood are thought to be born in the inner disk and came to present location by radial migration, which is most intense at the co-rotation resonance (CR) of the Galactic bar. In this work, we show evidence for the CR origin of SMR stars in LAMOST-Gaia by detecting six ridges and undulations in the phi versus Lz space coded by median VR, following a similar slope of -8 km/s kpc/deg. The slope is predicted by Monario et al.'s model for CR of a large and slow Galactic bar. For the first time, we show the variation of angular momentum with azimuths from -10 deg to 20 deg for two outer and broad undulations with negative VR around -18 km/s following this slope. The wave-like pattern with large amplitude outside CR and a wide peak of the second undulations indicate that minor merger of the Sagittarius dwarf galaxy with the disk might play a role besides the significant impact of CR of the Galactic bar.