The nucleosynthetic history of elements in the Galactic disk: [X/Fe] - age relations from high-precision spectroscopy

TL;DR

This study investigates the [X/Fe]-age relations of 24 elements in the Galactic disk using high-precision spectroscopy of solar twins, revealing distinct nucleosynthesis signatures and proposing stellar clocks for galactic evolution insights.

Contribution

It provides the first comprehensive [X/Fe]-age relations for 24 elements in the Galactic disk, utilizing high-precision data to enhance understanding of chemical evolution and nucleosynthesis processes.

Findings

Alpha-elements decrease with age, except for calcium.

Iron-peak elements show an initial increase then decrease in [X/Fe].

[Mg/Y] and [Al/Y] serve as precise stellar clocks.

Abstract

Context: The chemical composition of stars is intimately linked to the Galaxy formation and evolution. Aims: We aim to trace the chemical evolution of the Galactic disk through the inspection of the [X/Fe]-age relations of 24 species from C to Eu. Methods: Using high-resolution and high-signal-to-noise UVES spectra of nine solar twins, we obtained precise estimates of stellar ages and chemical abundances. These determinations have been integrated with additional accurate age and abundance determinations from recent spectroscopic studies of solar twins existing in the literature, comprising superb abundances with 0.01~dex precision. Based on this data set, we outlined the [X/Fe]-age relations over a time interval of 10~Gyr. Results: We present the [X/Fe] - age relations for 24 elements (C, O, Na, Mg, Al, Si, S, K, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Y, Ba, La, Ce, Nd, and Eu). Each different class of elements showed distinct evolution with time that relies on the different characteristics, rates and timescales of the nucleosynthesis' sites from which they are produced. The $\alpha$-elements are characterised by a [X/Fe] decrement as time goes on. Strikingly, an opposite behaviour is observed for Ca. The iron-peak elements show an early [X/Fe] increase followed by a decrease towards the youngest stars. The [X/Fe] for the n-capture elements decrease with age. We also found that both [Mg/Y] and [Al/Y] are precise stellar clocks, with [Al/Y] showing the steepest dependence with age. Conslusions: Knowledge of the [X/Fe]-age relations is a gold mine from which we can achieve a great understanding about the processes that governed the formation and evolution of the Milky Way. Through the reverse engineering of these relations we will be able to put strong constraints on the nature of the stellar formation history, the SNe rates, the stellar yields, and the variety of the SNe progenitors.