Zinc abundances in Galactic bulge field red giants: Implications for damped Lyman-α systems

Context. Zinc in stars is an important reference element because it is a proxy to Fe in studies of damped Lyman-alpha systems (DLAs), 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. Abundance studies in different stellar populations can give hints to the Zn production in different sites. Aims. 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-a systems, in order to better understand the chemical evolution in these environments. Methods. High-resolution spectra were obtained using FLAMES+UVES on the Very Large Telescope. We computed the in abundances using the ZnI lines at 4810.53 and 6362.34 angstrom. We considered the strong depression in the continuum of the Zn I 6362.34 angstrom line, which is caused by the wings of the Cat 6361.79 angstrom line suffering from autc)ionization. CN lines blending the ZnI 6362.34 angstrom line are also included in the calculations. Results. We find [Zn/FA2] = +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. When we take these corrections into account, the [Zn/Fe] vs. Weal of the DLAs Fall in the same region as the thick disk and bulge stars. Finally, we present a chemical evolution model of Zn enrichment in massive spheroids, representing a typical classical bulge evolution.