The Stellar Disk Structure Revealed by the Mono-age Populations of the LAMOST Red Clump Star Sample

Abstract

Understanding the structure of the Galactic disk is crucial for understanding the formation and evolutionary history of the Milky Way. This study examines the structure of the Galactic disk by analyzing a sample of 138,667 primary red clump (RC) stars from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope and Gaia data sets. We have categorized these RC stars into mono-age populations and investigated their spatial distributions within the R – Z plane, estimating scale heights and lengths through the fitting of their vertical and radial density profiles. Our analysis indicates that the vertical profiles of these mono-age populations fit a dual-component disk model, where both components exhibit significant flaring, particularly in the outer disk regions. Within a constant Galactocentric radius R , the scale heights of the first component, representing the morphologically thin disk, rise with age. In contrast, the scale heights of the second component, corresponding to the morphologically thick disk, remain comparatively stable across different age groups. Additionally, the radial density profiles of both disk components predominantly peak within a radial range of 7.5–8.5 kpc. These findings underscore the importance of age as a crucial factor in shaping the spatial distribution and structural evolution of the Galactic disk, offering valuable insights into its complex dynamics and history.

Keywords

• Milky Way disk
• Milky Way evolution
• Galaxy structure