Structural Parameters of the Thin Disk Population from Evolved Stars in Solar Neighborhood

TL;DR

This paper analyzes the spatial distribution of evolved stars in the solar neighborhood using Gaia DR3 data to determine the structural parameters of the thin disk, revealing scale height variations linked to stellar evolution.

Contribution

It provides new measurements of the scale heights of evolved stars in the solar neighborhood and explores their dependence on absolute magnitude, contributing to understanding Galactic disk structure.

Findings

Evolved stars' scale heights range from 200 to 600 pc.

Red clump stars have a scale height of approximately 295 pc.

Scale height variations reflect different stellar populations and Galactic evolution processes.

Abstract

This study investigates the structural parameters of the thin-disk population by analyzing the spatial distribution of evolved stars in the solar neighbourhood. From the $\it Gaia$ Data Release 3 database, about 39.1 million stars within 1 kpc and with relative parallax errors $\sigma_{\varpi}/\varpi\leq 0.10$ were selected. The photometric data was corrected for extinction using a Galactic dust map. The sample was refined by considering the color-magnitude region $M_{\rm G}\times (G_{\rm BP}-G_{\rm RP})_0$ associated with evolved stars, applying a stricter parallax error limit of $\sigma_{\varpi}/\varpi\leq 0.02$, and yielding 671,600 stars. The star sample was divided into 36 regions based on their Galactic coordinates, with evolved stars in the absolute magnitude range of $-1< M_{\rm G}~{\rm (mag)}\leq 4$ further split into five one-unit magnitude intervals. This led to 180 subgroups whose space density profiles were modelled using a single-component Galaxy model. The analysis shows that the space densities are in agreement with the literature and that the scale heights vary with $200<H~{\rm (pc)}<600$ interval to their absolute magnitudes. Red clump stars in the solar neighbourhood were also estimated to have a scale height of $295\pm10$ pc. These findings indicate that evolved stars with bright absolute magnitudes originate from the evolution of the early spectral-type stars with short scale height, while fainter ones come from the evolution of the intermediate spectral-type stars with large scale height, suggesting variations in scale height reflect the contribution of Galactic evolution processes.