Evidence for Corotation Origin of Super-metal-rich Stars in LAMOST-Gaia: Multiple Ridges with a Similar Slope in the ϕ versus L z Plane

Abstract

Super-metal-rich (SMR) stars in the solar neighborhood are thought to be born in the inner disk and come to their present location by radial migration, which is most intense at the corotation resonance (CR) of the Galactic bar. In this work, we show evidence for the CR origin of SMR stars in the Large Sky Area Multi-Object Fiber Spectroscopic Telescope and Gaia by detecting six ridges and undulations in the ϕ versus L z space coded by median V R, following a similar slope of −8 km s−1 kpc deg−1. 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 in the angular momentum with azimuths from −10° to 20° for two outer and broad undulations with negative V R around − 18 km s−1 following this slope. The wave-like pattern with large amplitude outside CR and a wide peak of the second undulation indicate that minor merger of the Sagittarius dwarf galaxy with the disk might play a role besides the significant impact of the CR of the Galactic bar.