Red Giant Clump in the Tycho-2 Catalogue

TL;DR

This study uses Tycho-2 and 2MASS data to identify and analyze a large sample of red giant clump stars within 350 parsecs, revealing their distribution, motions, and age-related differences in the Galactic disk.

Contribution

It provides a comprehensive, unbiased catalog of RGC stars with detailed spatial and kinematic analysis, including the discovery of young RGC stars and the Sun's position relative to the Galactic plane.

Findings

Identified 97,348 RGC stars within 350 pc of the Sun.

Detected a significant fraction of young RGC stars younger than 1 Gyr.

Found the Sun is approximately 13 pc above the Galactic plane.

Abstract

The Tycho-2 proper motions and Tycho-2 and 2MASS photometry are used to select 97348 red giant clump (RGC) stars. The interstellar extinction and photometric distance are calculated for each of the stars. The selected stars are shown to form a selection-unbiased sample of RGC stars within about 350 pc of the Sun with the addition of more distant stars. The distribution of the selected stars in space and their motion are consistent with the assumption that the RGC contains Galactic disk stars with various ages and metallicities, including a significant fraction of stars younger than 1 Gyr with masses of more than 2 $M_{\odot}$. These young stars show differences of their statistical characteristics from those of older RGC stars, including differences in the variations of their distribution density with distance from the Galactic plane and in the dispersion of their velocities found using radial velocities and proper motions. The Sun has been found to rise above the Galactic plane by $13\pm1$ pc. The distribution density of the stars under consideration in space is probably determined by the Local Spiral Arm and the distribution of absorbing matter in the plane of the Gould Belt.