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VINTERGATAN-GM : The cosmological imprints of early mergers on Milky-Way-mass galaxies

Rey, Martin P. LU ; Agertz, Oscar LU ; Starkenburg, Tjitske K. ; Renaud, Florent LU ; Joshi, Gandhali D. ; Pontzen, Andrew ; Martin, Nicolas F. ; Feuillet, Diane K. LU orcid and Read, Justin I. (2023) In Monthly Notices of the Royal Astronomical Society 521(1). p.995-1012
Abstract

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... (More)

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.

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author
; ; ; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
galaxies: formation, galaxies: kinematics and dynamics, Galaxy: formation, Galaxy: halo, methods: numerical
in
Monthly Notices of the Royal Astronomical Society
volume
521
issue
1
pages
18 pages
publisher
Oxford University Press
external identifiers
  • scopus:85161604592
ISSN
0035-8711
DOI
10.1093/mnras/stad513
language
English
LU publication?
yes
id
600f86db-da4c-4853-8ae5-453395087143
date added to LUP
2023-08-22 11:33:36
date last changed
2023-08-22 11:33:36
@article{600f86db-da4c-4853-8ae5-453395087143,
  abstract     = {{<p>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 (M<sub>200</sub> ≈ 10<sup>12</sup> M<sub>☉</sub>), 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.</p>}},
  author       = {{Rey, Martin P. and Agertz, Oscar and Starkenburg, Tjitske K. and Renaud, Florent and Joshi, Gandhali D. and Pontzen, Andrew and Martin, Nicolas F. and Feuillet, Diane K. and Read, Justin I.}},
  issn         = {{0035-8711}},
  keywords     = {{galaxies: formation; galaxies: kinematics and dynamics; Galaxy: formation; Galaxy: halo; methods: numerical}},
  language     = {{eng}},
  number       = {{1}},
  pages        = {{995--1012}},
  publisher    = {{Oxford University Press}},
  series       = {{Monthly Notices of the Royal Astronomical Society}},
  title        = {{VINTERGATAN-GM : The cosmological imprints of early mergers on Milky-Way-mass galaxies}},
  url          = {{http://dx.doi.org/10.1093/mnras/stad513}},
  doi          = {{10.1093/mnras/stad513}},
  volume       = {{521}},
  year         = {{2023}},
}