Simulations of minor mergers - II. The phase-space structure of thick discs
Open accessAbstract
We analyse the phase-space structure of simulated thick discs that are the result of a 5:1 mass-ratio merger between a disc galaxy and a satellite. Our main goal is to establish what would be the imprints of a merger origin for the Galactic thick disc. We find that the spatial distribution predicted for thick-disc stars is asymmetric, seemingly in agreement with recent observations of the Milky Way thick disc. Near the Sun, the accreted stars are expected to rotate more slowly, to have broad velocity distributions and to occupy preferentially the wings of the line-of-sight velocity distributions. The majority of the stars in our model thick discs have low eccentricity orbits (in clear reference to the pre-existing heated disc) which give rise to a characteristic (sinusoidal) pattern for their line-of-sight velocities as a function of galactic longitude. The z-component of the angular momentum of thick-disc stars provides a clear discriminant between stars from the pre-existing disc and those from the satellite, particularly at large radii. These results are robust against the particular choices of initial conditions made in our simulations.
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Comparison of Gaia kinematics with simulations suggests that the Gaia-Enceladus merger was counter-rotating and that its initial inclination was approximately 30°.
“a coarse comparison of the Gaia kinematical data with existing simulations of the merger of a disk galaxy with a massive disky satellite (Villalobos & Helmi 2008, 2009), as shown in Figure 8, suggests that the merger was counter-rotating because the mean rotational motion of associated halo stars in the solar vicinity is (slightly) retrograde”
From Streams, Substructures, and the Early History of the Milky Way (2020) · cites this paper as Villalobos & Helmi 2009
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Galactic Dynamics: Second Edition
Binney, J., & Tremaine, S. (2008) · doi:10.1515/9781400828722 · Cited by 4,375 · cited 1× · see citing works
“Thus as the satellite gets disrupted, its stars remain somewhat constrained in azimuth, which results in the observed m = 2 deviations, in rather close analogy to what happens as a result of the radial orbit instability (Binney & Tremaine 2008).”
ResultDeciphering the Last Major Invasion of the Milky Way
Gilmore, G., Wyse, R. F. G., & Norris, J. E. (2002) · The Astrophysical Journal · doi:10.1086/342363 · Cited by 203 · see citing works
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Research works printed but not linked: 3
- Binney J., Tremaine S., 2008, Galactic Dynamics: 2nd Edi- tion. Princeton University Press, Princeton, NJ USA
- W. H., Teukolsky S. A., Vetterling W. T., Flannery B. P., 1992, Numerical recipes in C. The art of scientific computing. Cambridge: University Press
- Wyse R. F. G., 2004, ArXiv Astrophysics e-prints
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The merger that led to the formation of the Milky Way’s inner stellar halo and thick disk
Helmi, A., Babusiaux, C., Koppelman, H. H., Massari, D., Veljanoski, J., & Brown, A. G. A. (2018) · Nature · doi:10.1038/s41586-018-0625-x · Cited by 1,235 · see citing works
Self-citationCo-formation of the disc and the stellar halo★
Belokurov, V, Erkal, D., Evans, N. W., Koposov, S. E., & Deason, A. J. (2018) · Monthly Notices of the Royal Astronomical Society · doi:10.1093/mnras/sty982 · Cited by 1,020 · see citing works
Streams, Substructures, and the Early History of the Milky Way
Helmi, A. (2020) · Annual Review of Astronomy and Astrophysics · doi:10.1146/annurev-astro-032620-021917 · Cited by 407 · see citing works
Self-citationDi Matteo, P., Haywood, M., Lehnert, M. D., Katz, D., Khoperskov, S., Snaith, O. N., Gómez, A., & Robichon, N. (2019) · Astronomy & Astrophysics · doi:10.1051/0004-6361/201834929 · Cited by 222 · see citing works
- Authors
- Villalobos, Á., & Helmi, A.
- Affiliations
- University of Groningen (NL)
- Corresponding author
- Villalobos, Álvaro
- ORCID
- Helmi, Amina
- Venue
- Monthly Notices of the Royal Astronomical Society
- Publisher
- Oxford University Press (OUP)
- Published
- 2009-10-11
- Volume
- 399
- Issue
- 1
- Pages
- 166-176
- ISSN
- 0035-8711 (ISSN-L)
- 1365-2966
- OpenAlex
- W2094866179
- Cited by
- 56
- References
- 2
- Citations by year
- 2026: 1 · 2025: 2 · 2024: 1 · 2023: 2 · 2022: 1 · 2021: 3 · 2020: 6 · 2019: 2 · 2018: 6 · 2017: 4 · 2016: 4 · 2015: 5 · 2014: 2 · 2013: 2 · 2012: 6
- FWCI
- 2.52
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- Monthly Notices of the Royal Astronomical Society (publishedVersion)
- arXiv (Cornell University) (submittedVersion)
- University of Groningen research database (University of Groningen / Centre for Information Technology) (submittedVersion, other-oa)
- arXiv (Cornell University)
- Funders
- Rijksuniversiteit Groningen
- Nederlandse Organisatie voor Wetenschappelijk Onderzoek
- Topics
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Stellar, planetary, and galactic studies
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Galaxies: Formation, Evolution, Phenomena
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Astrophysical Phenomena and Observations
- Keywords
- minor mergers, thick disk, Galactic thick disc, phase space structure, satellite accretion, line-of-sight velocity distribution, angular momentum, orbital eccentricity, Milky Way, stellar kinematics
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