Vertical distribution of Galactic disk stars IV - AMR and AVR from clump giants

TL;DR

This study analyzes a large sample of clump giants to understand the vertical distribution, metallicity gradients, and age-velocity relations in the Galactic disk, revealing new insights into its structure and evolution.

Contribution

It provides a comprehensive analysis of 891 clump giants, including new measurements and revisiting the Galactic thin disk's properties with a kinematically unbiased sample.

Findings

Metallicity distribution differs from dwarfs, with fewer metal-rich stars.

Evidence for a vertical metallicity gradient of -0.31 dex/kpc.

Age-velocity relation shows saturation of velocity dispersions at 5 Gyr.

Abstract

We present the parameters of 891 stars, mostly clump giants, including atmospheric parameters, distances, absolute magnitudes, spatial velocities, galactic orbits and ages. One part of this sample consists of local giants, within 100 pc, with atmospheric parameters either estimated from our spectroscopic observations at high resolution and high signal-to-noise ratio, or retrieved from the literature. The other part of the sample includes 523 distant stars, which we have estimated atmospheric parameters from high resolution but low signal-to-noise Echelle spectra. This new sample is kinematically unbiased, with well-defined boundaries in magnitude and colours. We revisit the basic properties of the Galactic thin disk as traced by clump giants. We find the metallicity distribution to be different from that of dwarfs, with less metal-rich stars. We find evidence for a vertical metallicity gradient of -0.31 dex/kpc and for a transition at 4-5 Gyr in both the metallicity and velocities. The age - metallicity relation (AMR), which exhibits a very low dispersion, increases smoothly from 10 to 4 Gyr, with a steeper increase for younger stars. The age-velocity relation (AVR) is characterized by the saturation of the V and W dispersions at 5 Gyr, and continuous heating in U.