Oscar Agertz
Associate Professor / Senior university lecturer / Wallenberg Academy Fellow
VINTERGATAN-GM : The cosmological imprints of early mergers on Milky-Way-mass galaxies
Author
Summary, in English
We present a new suite of cosmological zoom-in hydrodynamical (≈ 20 pc spatial resolution) simulations of Milky-Way mass galaxies to study how a varying mass ratio for a Gaia-Sausage-Enceladus (GSE) progenitor impacts the z = 0 chemodynamics of halo stars. Using the genetic modification approach, we create five cosmological histories for a Milky-Way-mass dark matter halo (M200 ≈ 1012 M☉), incrementally increasing the stellar mass ratio of a z ≈ 2 merger from 1:25 to 1:2, while fixing the galaxy’s final dynamical, stellar mass, and large-scale environment. We find markedly different morphologies at z = 0 following this change in early history, with a growing merger resulting in increasingly compact and bulge-dominated galaxies. Despite this structural diversity, all galaxies show a radially biased population of inner halo stars like the Milky-Way’s GSE which, surprisingly, has a similar magnitude, age, [Fe/H], and [α/Fe] distribution whether the z ≈ 2 merger is more minor or major. This arises because a smaller ex-situ population at z ≈ 2 is compensated by a larger population formed in an earlier merger-driven starburst whose contribution to the GES can grow dynamically over time, and with both populations strongly overlapping in the [Fe/H] − [α/Fe] plane. Our study demonstrates that multiple high-redshift histories can lead to similar z = 0 chemodynamical features in the halo, highlighting the need for additional constraints to distinguish them, and the importance of considering the full spectrum of progenitors when interpreting z = 0 data to reconstruct our Galaxy’s past.
Department/s
- Astrophysics
- eSSENCE: The e-Science Collaboration
Publishing year
2023
Language
English
Pages
995-1012
Publication/Series
Monthly Notices of the Royal Astronomical Society
Volume
521
Issue
1
Document type
Journal article
Publisher
Oxford University Press
Topic
- Astronomy, Astrophysics and Cosmology
Keywords
- galaxies: formation
- galaxies: kinematics and dynamics
- Galaxy: formation
- Galaxy: halo
- methods: numerical
Status
Published
ISBN/ISSN/Other
- ISSN: 0035-8711