In the thick of it: metal-poor disc stars in RAVE

Kordopatis, G.; Gilmore, G.; Wyse, R.F.G.; Steinmetz, M.; Siebert, A.; Bienaymé, O.; McMillan, P. J.; Minchev, I.; Zwitter, T.; Gibson, B. K.; Seabroke, G.; Grebel, E. K.; Bland-Hawthorn, J.; Boeche, C.; Freeman, K. C.; Munari, U.; Navarro, J. F.; Parker, Q.; Reid, W. A.; Siviero, A.

Abstract

By selecting in the Radial Velocity Experiment-fourth data release (RAVE-DR4) survey the stars located between 1 and 2 kpc above the Galactic plane, we question the consistency of the simplest three-component model (thin disc, thick disc and halo) for the Milky Way. We confirm that the metallicity and azimuthal velocity distribution functions of the thick disc are not Gaussian. In particular, we find that the thick disc has an extended metallicity tail going at least down to [M/H] = ‒2 dex, contributing roughly 3 per cent of the entire thick disc population and having a shorter scalelength compared to the canonical thick disc. The mean azimuthal velocity of these metal-poor stars allows us to estimate the correlation between the metallicity ([M/H]) and the orbital velocity (Vϕ), which is an important constraint on the formation mechanisms of the Galactic thick disc. Given our simple approach, we find ∂Vϕ/∂[M/H]≈ 50 km s−1 dex−1, which is in very good agreement with previous literature values. We complete the study with a brief discussion on the implications of the formation scenarios for the thick disc and suggest that given the above-mentioned characteristics, a thick disc mainly formed by radial migration mechanisms seems unlikely.

Citation

Kordopatis, G., Gilmore, G., Wyse, R., Steinmetz, M., Siebert, A., Bienaymé, O., …Siviero, A. (2013). In the thick of it: metal-poor disc stars in RAVE. Monthly notices of the Royal Astronomical Society, 436(4), 3231-3246. https://doi.org/10.1093/mnras/stt1804

• Journal Article Type: Article
• Acceptance Date: Sep 23, 2013
• Online Publication Date: Oct 15, 2013
• Publication Date: Dec 21, 2013
• Deposit Date: Apr 25, 2016
• Publicly Available Date: Apr 25, 2016
• Journal: Monthly notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 436
• Issue: 4
• Pages: 3231-3246
• DOI: https://doi.org/10.1093/mnras/stt1804
• Keywords: Galaxy : abundances, Galaxy : disc, Galaxy : kinematics and dynamics, Galaxy : stellar content, Galaxy : structure
• Public URL: https://hull-repository.worktribe.com/output/436916
• Publisher URL: http://mnras.oxfordjournals.org/content/436/4/3231
• Additional Information: This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly notices of the Royal Astronomical Society following peer review. The version of record G. Kordopatis, G. Gilmore, R. F. G. Wyse, M. Steinmetz, A. Siebert, O. Bienaymé, P. J. McMillan, I. Minchev, T. Zwitter, B. K. Gibson, G. Seabroke, E. K. Grebel, J. Bland-Hawthorn, C. Boeche, K. C. Freeman, U. Munari, J. F. Navarro, Q. Parker, W. A. Reid, and A. Siviero. In the thick of it: metal-poor disc stars in RAVE. MNRAS (December 21, 2013) Vol. 436 3231-3246 doi:10.1093/mnras/stt1804 first published online October 15, 2013 is available online at: http://mnras.oxfordjournals.org/content/436/4/3231.