Abundances of disk and bulge giants from high-resolution optical spectra : IV. Zr, La, Ce, Eu
(2019) In Astronomy & Astrophysics 631.- Abstract
- Context. Observations of the Galactic bulge suggest that the disk formed through secular evolution rather than gas dissipation and/or mergers, as previously believed. This would imply very similar chemistry in the disk and bulge. Some elements, such as the α-elements, are well studied in the bulge, but others like the neutron-capture elements are much less well explored. Stellar mass and metallicity are factors that affect the neutron-capture process. Due to this, the enrichment of the ISM and the abundance of neutron-capture elements vary with time, making them suitable probes for Galactic chemical evolution.
Aims. In this work, we make a differential comparison of neutron-capture element abundances... (More) - Context. Observations of the Galactic bulge suggest that the disk formed through secular evolution rather than gas dissipation and/or mergers, as previously believed. This would imply very similar chemistry in the disk and bulge. Some elements, such as the α-elements, are well studied in the bulge, but others like the neutron-capture elements are much less well explored. Stellar mass and metallicity are factors that affect the neutron-capture process. Due to this, the enrichment of the ISM and the abundance of neutron-capture elements vary with time, making them suitable probes for Galactic chemical evolution.
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. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/95123ba6-97a3-428a-aa90-9b40d6af0498
- author
- Forsberg, R. LU ; Jönsson, H. LU ; Ryde, N. LU and Matteucci, F.
- organization
- publishing date
- 2019-11
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- stars: abundances, Galaxy: bulge, solar neighborhood, Galaxy: evolution
- in
- Astronomy & Astrophysics
- volume
- 631
- article number
- A113
- pages
- 15 pages
- publisher
- EDP Sciences
- external identifiers
-
- scopus:85082694785
- ISSN
- 1432-0746
- DOI
- 10.1051/0004-6361/201936343
- project
- Abundances of Neutron-Capture Elements in the Galactic Bulge and Disk from High-Resolution Spectra
- language
- English
- LU publication?
- yes
- id
- 95123ba6-97a3-428a-aa90-9b40d6af0498
- date added to LUP
- 2021-03-10 16:32:14
- date last changed
- 2024-04-18 04:22:30
@article{95123ba6-97a3-428a-aa90-9b40d6af0498, abstract = {{<i>Context</i>. Observations of the Galactic bulge suggest that the disk formed through secular evolution rather than gas dissipation and/or mergers, as previously believed. This would imply very similar chemistry in the disk and bulge. Some elements, such as the <i>α</i>-elements, are well studied in the bulge, but others like the neutron-capture elements are much less well explored. Stellar mass and metallicity are factors that affect the neutron-capture process. Due to this, the enrichment of the ISM and the abundance of neutron-capture elements vary with time, making them suitable probes for Galactic chemical evolution.<br/><br/><i>Aims</i>. 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.<br/><br/><i>Methods</i>. 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.<br/><br/><i>Results</i>. 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 <i>α</i>-elements in all populations.<br/><br/><i>Conclusions</i>. 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.}}, author = {{Forsberg, R. and Jönsson, H. and Ryde, N. and Matteucci, F.}}, issn = {{1432-0746}}, keywords = {{stars: abundances; Galaxy: bulge; solar neighborhood; Galaxy: evolution}}, language = {{eng}}, publisher = {{EDP Sciences}}, series = {{Astronomy & Astrophysics}}, title = {{Abundances of disk and bulge giants from high-resolution optical spectra : IV. Zr, La, Ce, Eu}}, url = {{http://dx.doi.org/10.1051/0004-6361/201936343}}, doi = {{10.1051/0004-6361/201936343}}, volume = {{631}}, year = {{2019}}, }