The origin of the Milky Way's halo age distribution

Carollo, Daniela; Tissera, Patricia B.; Beers, Timothy C.; Gudin, Dmitrii; Gibson, Brad K.; Freeman, Ken C.; Monachesi, Antonela

Abstract

© 2018. The American Astronomical Society.. We present an analysis of the radial age gradients for the stellar halos of five Milky Way (MW) mass-sized systems simulated as part of the Aquarius Project. The halos show a diversity of age trends, reflecting their different assembly histories. Four of the simulated halos possess clear negative age gradients, ranging from approximately -7 to -19 Myr kpc-1, shallower than those determined by recent observational studies of the Milky Way's stellar halo. However, when restricting the analysis to the accreted component alone, all of the stellar halos exhibit a steeper negative age gradient with values ranging from -8 to -32 Myr kpc-1, closer to those observed in the Galaxy. Two of the accretion-dominated simulated halos show a large concentration of old stars in the center, in agreement with the Ancient Chronographic Sphere reported observationally. The stellar halo that best reproduces the current observed characteristics of the age distributions of the Galaxy is that formed principally by the accretion of small satellite galaxies. Our findings suggest that the hierarchical clustering scenario can reproduce the MW's halo age distribution if the stellar halo was assembled from accretion and the disruption of satellite galaxies with dynamical masses less than ∼109.5M, and a minimal in situ contribution.

Citation

Carollo, D., Tissera, P. B., Beers, T. C., Gudin, D., Gibson, B. K., Freeman, K. C., & Monachesi, A. (2018). The origin of the Milky Way's halo age distribution. Astrophysical journal. Letters, 859(1), L7. https://doi.org/10.3847/2041-8213/aac2dc

• Journal Article Type: Article
• Acceptance Date: May 2, 2018
• Online Publication Date: May 18, 2018
• Publication Date: May 20, 2018
• Deposit Date: Jun 26, 2018
• Publicly Available Date: Jun 27, 2018
• Journal: Astrophysical Journal Letters
• Print ISSN: 2041-8205
• Electronic ISSN: 2041-8213
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 859
• Issue: 1
• Article Number: L7
• Pages: L7
• DOI: https://doi.org/10.3847/2041-8213/aac2dc
• Keywords: Galaxy: formation; Galaxy: halo; Galaxy: stellar content; Galaxy: structure; Stars: Population II
• Public URL: https://hull-repository.worktribe.com/output/888740
• Publisher URL: http://iopscience.iop.org/article/10.3847/2041-8213/aac2dc/meta
• Additional Information: Journal title: The Astrophysical Journal; Article type: paper; Article title: The Origin of the Milky Way's Halo Age Distribution; Copyright information: © 2018. The American Astronomical Society.; License information: cc-by Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.; Date received: 2017-12-28; Date accepted: 2018-05-02; Online publication date: 2018-05-18