Abundances of disk and bulge giants from high-resolution optical spectra : IV. Zr, La, Ce, Eu
Summary, in English
Aims. In this work, we make a differential comparison of neutron-capture element abundances determined in the local disk(s) and the bulge, focusing on minimising possible systematic effects in the analysis, with the aim of finding possible differences/similarities between the populations.
Methods. Abundances are determined for Zr, La, Ce, and Eu in 45 bulge giants and 291 local disk giants, from high-resolution optical spectra. The abundances are determined by fitting synthetic spectra using the SME-code. The disk sample is separated into thin- and thick-disk components using a combination of abundances and kinematics.
Results. We find flat Zr, La, and Ce trends in the bulge, with a ~0.1 dex higher La abundance compared with the disk, possibly indicating a higher s-process contribution for La in the bulge. [Eu/Fe] decreases with increasing [Fe/H], with a plateau at around [Fe/H] ~−0.4, pointing at similar enrichment to α-elements in all populations.
Conclusions. We find that the r-process dominated the neutron-capture production at early times both in the disks and bulge. Further, [La/Eu] ratios for the bulge are systematically higher than for the thick disk, pointing to either a) a different amount of SN II or b) a different contribution of the s-process in the two populations. Considering [(La+Ce)/Zr], the bulge and the thick disk follow each other closely, suggesting a similar ratio of high-to-low-mass asymptotic giant branch stars.
- Astronomy, Astrophysics and Cosmology
- stars: abundances
- Galaxy: bulge
- solar neighborhood
- Galaxy: evolution
- Abundances of Neutron-Capture Elements in the Galactic Bulge and Disk from High-Resolution Spectra
- ISSN: 1432-0746