Zinc abundances in Galactic bulge field red giants: implications for DLA systems

TL;DR

This study measures zinc abundances in 56 Galactic bulge giants using high-resolution spectra to compare chemical evolution with DLA systems and other stellar populations, revealing a decreasing [Zn/Fe] trend at higher metallicities.

Contribution

It provides new zinc abundance data for bulge giants and compares these with DLA systems and models, enhancing understanding of chemical evolution in galactic bulges.

Findings

[Zn/Fe] increases at low metallicity, then decreases at high metallicity.

Most high-metallicity bulge stars have low [Zn/Fe] values.

Comparison with DLA systems suggests similar chemical evolution patterns.

Abstract

Zinc in stars is an important reference element because it is a proxy to Fe in studies of damped Lyman-alpha systems, permitting a comparison of chemical evolution histories of bulge stellar populations and DLAs. In terms of nucleosynthesis, it behaves as an alpha element because it is enhanced in metal-poor stars. The aim of this work is to derive the iron-peak element Zn abundances in 56 bulge giants from high resolution spectra. These results are compared with data from other bulge samples, as well as from disk and halo stars, and damped Lyman-alpha systems, in order to better understand the chemical evolution in these environments. High-resolution spectra were obtained using FLAMES+UVES on the Very Large Telescope. We find [Zn/Fe]=+0.24+-0.02 in the range -1.3 < [Fe/H] < -0.5 and [Zn/Fe]=+0.06+-0.02 in the range -0.5 < [Fe/H] < -0.1, whereas for [Fe/H] > -0.1, it shows a spread of -0.60 < [Zn/Fe] < +0.15, with most of these stars having low [Zn/Fe]<0.0. These low zinc abundances at the high metallicity end of the bulge define a decreasing trend in [Zn/Fe] with increasing metallicities. A comparison with Zn abundances in DLA systems is presented, where a dust-depletion correction was applied for both Zn and Fe. Finally, we present a chemical evolution model of Zn enrichment in massive spheroids, representing a typical classical bulge.