Asymmetric metallicity patterns in the stellar velocity space with RAVE

Antoja, T.; Kordopatis, G.; Helmi, A.; Monari, G.; Famaey, B.; Wyse, R. F. G.; Grebel, E. K.; Steinmetz, M.; Bland-Hawthorn, J.; Gibson, B. K.; Bienaymé, O.; Navarro, J. F.; Parker, Q. A.; Reid, W.; Seabroke, G.; Siebert, A.; Siviero, A.; Zwitter, T.

Abstract

© ESO, 2017. Context. The chemical abundances of stars encode information on their place and time of origin. Stars formed together in e.g. a cluster, should present chemical homogeneity. Also disk stars influenced by the effects of the bar and the spiral arms might have distinct chemical signatures depending on the type of orbit that they follow, e.g. from the inner versus outer regions of the Milky Way. Aims. We explore the correlations between velocity and metallicity and the possible distinct chemical signatures of the velocity over-densities of the local Galactic neighbourhood. Methods. We use the large spectroscopic survey RAVE and the Geneva Copenhagen Survey. We compare the metallicity distribution of regions in the velocity plane (vR,vφ) with that of their symmetric counterparts (-vR,vφ). We expect similar metallicity distributions if there are no tracers of a sub-population (e.g. a dispersed cluster, accreted stars), if the disk of the Galaxy is axisymmetric, and if the orbital effects of the bar and the spiral arms are weak. Results. We find that the metallicity-velocity space of the solar neighbourhood is highly patterned. A large fraction of the velocity plane shows differences in the metallicity distribution when comparing symmetric vRregions. The typical differences in the median metallicity are of 0.05 dex with statistical significant of at least 95% confidence, and with values up to 0.6 dex. For stars with low azimuthal velocity vφ, the ones moving outwards. These include stars in the Hercules and Hyades moving groups and other velocity branch-like structures. For higher vφ, the stars moving inwards have higher metallicity than those moving outwards. We have also discovered a positive gradient in vφwith respect to metallicity at high metallicities, apart from the two known positive and negative gradients for the thick and thin disks. Conclusions. The most likely interpretation of the metallicity asymmetry is that it is mainly due to the orbital effects of the Galactic bar and the radial metallicity gradient of the disk. We present a simulation that supports this idea.

Citation

Antoja, T., Kordopatis, G., Helmi, A., Monari, G., Famaey, B., Wyse, R. F. G., Grebel, E. K., Steinmetz, M., Bland-Hawthorn, J., Gibson, B. K., Bienaymé, O., Navarro, J. F., Parker, Q. A., Reid, W., Seabroke, G., Siebert, A., Siviero, A., & Zwitter, T. (2017). Asymmetric metallicity patterns in the stellar velocity space with RAVE. Astronomy and Astrophysics, 601, A59. https://doi.org/10.1051/0004-6361/201629387

• Journal Article Type: Article
• Acceptance Date: Feb 14, 2017
• Online Publication Date: Apr 28, 2017
• Publication Date: 2017-05
• Deposit Date: Jun 28, 2018
• Publicly Available Date: Jul 11, 2018
• Journal: Astronomy and Astrophysics
• Print ISSN: 0004-6361
• Publisher: EDP Sciences
• Peer Reviewed: Peer Reviewed
• Volume: 601
• Article Number: A59
• Pages: A59
• DOI: https://doi.org/10.1051/0004-6361/201629387
• Keywords: Galaxy: kinematics and dynamics; Galaxy: structure; Galaxy: disk; Galaxy: evolution
• Public URL: https://hull-repository.worktribe.com/output/888882
• Publisher URL: https://www.aanda.org/component/article?access=doi&doi=10.1051/0004-6361/201629387
• Related Public URLs: https://hydra.hull.ac.uk/resources/hull:14508
• Contract Date: Jun 28, 2018