Is there plenty of metal-poor stars with planets in the Galactic thick disk?

TL;DR

This study uses spectroscopic analysis to explore the relationship between stellar chemical composition and planet occurrence, revealing a higher incidence of planets among metal-poor thick disk stars compared to thin disk stars.

Contribution

It introduces a chemical approach based on [alpha/Fe] ratios to distinguish stellar populations and links chemical composition to planet hosting likelihood.

Findings

Higher planet occurrence in metal-poor thick disk stars

Chemical composition influences planet formation more than Galactic birthplace

Alpha-enhanced stars at high metallicity share thick disk characteristics

Abstract

We performed an uniform spectroscopic analysis of 1111 FGK dwarfs observed as part of the HARPS GTO planet search program. We applied a purely chemical approach, based on [alpha/Fe] ratio, to distinguish the various stellar components in the Galaxy. Apart from the well known Galactic thick and thin disks, we separated an alpha-enhanced stellar family at super-solar metallicities. The metal-rich high-alpha stars have orbits similar to the thin disk stars, but they are similar to thick disk stars in terms of age. Our data indicate that the incidence of stars with planets are greater among the chemically separated thick disk stars with [Fe/H] < -0.3 dex than they are among thin disk stars in the same [Fe/H] interval. Our results allow us to suppose that a certain chemical composition, and not the Galactic birth place of the stars, is the causative factor for that.