期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 486, 期 3, 页码 3180-3202出版社
OXFORD UNIV PRESS
DOI: 10.1093/mnras/sty1609
关键词
Galaxy: evolution; Galaxy: formation; globular clusters: general; Galaxy: halo; Galaxy: stellar content; galaxies: star formation
资金
- German Research Foundation (DFG) [KR4801/1-1]
- European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme via the ERC Starting Grant MUSTANG [714907]
- ERC under the European Union's Horizon 2020 research and innovation programme via the ERC Consolidator GrantMulti-Pop [646928]
- International Max Planck Research School for Astronomy and Cosmic Physics at the University of Heidelberg (IMPRS-HD)
- STFC capital grants [ST/H008519/1, ST/K00087X/1]
- STFC DiRAC Operations grant [ST/K003267/1]
- Durham University
- BIS National E-infrastructure capital grant [ST/K00042X/1]
- Royal Society
- LJMUs Faculty of Engineering and Technology
- STFC [ST/R002371/1, ST/R001049/1, ST/M007618/1, ST/I00162X/1, ST/H008519/1, ST/R000832/1, ST/K00042X/1, ST/R00689X/1, ST/T001372/1, ST/S002529/1, ST/M007065/1, ST/M007006/1, ST/P002293/1, ST/R001006/1, ST/M007073/1, ST/M006948/1, ST/R001014/1, ST/T001569/1, ST/T001348/1, ST/T001550/1] Funding Source: UKRI
We use the age-metallicity distribution of 96 Galactic globular clusters (GCs) to infer the formation and assembly history of the Milky Way (MW), culminating in the reconstruction of its merger tree. Based on a quantitative comparison of the Galactic GC population to the 25 cosmological zoom-in simulations of MW-mass galaxies in the E-MOSAICS project, which self-consistently model the formation and evolution of GC populations in a cosmological context, we find that the MW assembled quickly for its mass, reaching {25, 50} per cent of its present-day halo mass already at z = {3, 1.5} and half of its present-day stellar mass at z = 1.2. We reconstruct the MW's merger tree from its GC age-metallicity distribution, inferring the number of mergers as a function of mass ratio and redshift. These statistics place the MW's assembly rate among the 72th-94th percentile of the E-MOSAICS galaxies, whereas its integrated properties (e.g. number of mergers, halo concentration) match the median of the simulations. We conclude that the MW has experienced no major mergers (mass ratios > 1:4) since z similar to 4, sharpening previous limits of z similar to 2. We identify three massive satellite progenitors and constrain their mass growth and enrichment histories. Two are proposed to correspond to Sagittarius (a few 10(8) M-circle dot) and the GCs formerly associated with Canis Major (similar to 10(9)M(circle dot)). The third satellite has no known associated relic and was likely accreted between z = 0.6 and 1.3. We name this enigmatic galaxy Kraken and propose that it is the most massive satellite (M-* similar to 2 x 10(9)M(circle dot)) ever accreted by the MW. We predict that similar to 40 per cent of the Galactic GCs formed ex situ (in galaxies with masses M-* = 2 x 10(7)-2 x 10(9)M(circle dot)), with 6 +/- 1 being former nuclear clusters.
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