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Auriga Streams III : the mass–metallicity relation does not rule out tidal mass-loss in Local Group satellites

Riley, Alexander H. LU orcid ; Bieri, Rebekka ; Deason, Alis J. ; Shipp, Nora ; Simpson, Christine M. ; Fragkoudi, Francesca ; Gómez, Facundo A. ; Grand, Robert J.J. and Marinacci, Federico (2026) In Monthly Notices of the Royal Astronomical Society 546(3).
Abstract

The mass–metallicity relation is a fundamental galaxy scaling law that has been extended to the faintest systems in the Local Group. We show that the small scatter in this relation, which has been used to argue against tidal mass-loss in Local Group satellites, is consistent with the level of disruption in the Auriga simulations. For every accreted system in Auriga, we compute stellar masses and metallicities two ways: considering the total system (bound + lost material) and only considering the progenitor. Accreted systems in Auriga have a tight relation between total stellar mass and metallicity, with scatter at a fixed stellar mass driven by age. When only considering the progenitor, the tidally evolved mass–metallicity relation has... (More)

The mass–metallicity relation is a fundamental galaxy scaling law that has been extended to the faintest systems in the Local Group. We show that the small scatter in this relation, which has been used to argue against tidal mass-loss in Local Group satellites, is consistent with the level of disruption in the Auriga simulations. For every accreted system in Auriga, we compute stellar masses and metallicities two ways: considering the total system (bound + lost material) and only considering the progenitor. Accreted systems in Auriga have a tight relation between total stellar mass and metallicity, with scatter at a fixed stellar mass driven by age. When only considering the progenitor, the tidally evolved mass–metallicity relation has similar scatter (~0.27 dex) as observed for the Local Group satellites (~0.23 dex). Satellites that lie above the evolved relation have experienced substantial mass-loss and typically have low metallicity for their total stellar mass. Even satellites that fall exactly on the evolved relation can lose over half of their stellar mass. Only satellites substantially below the evolved relation are reliably intact. Based on their offset from the observed relation, we predict which Milky Way and M31 satellites have tidal tails waiting to be discovered.

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author
; ; ; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
galaxies: evolution, galaxies: formation, Galaxy: halo, Local Group
in
Monthly Notices of the Royal Astronomical Society
volume
546
issue
3
article number
stag029
publisher
Oxford University Press
external identifiers
  • scopus:105029968179
ISSN
0035-8711
DOI
10.1093/mnras/stag029
language
English
LU publication?
yes
id
b8287147-3a87-4a7b-ba73-08209ca5afd5
date added to LUP
2026-04-16 13:26:19
date last changed
2026-04-16 13:27:19
@article{b8287147-3a87-4a7b-ba73-08209ca5afd5,
  abstract     = {{<p>The mass–metallicity relation is a fundamental galaxy scaling law that has been extended to the faintest systems in the Local Group. We show that the small scatter in this relation, which has been used to argue against tidal mass-loss in Local Group satellites, is consistent with the level of disruption in the Auriga simulations. For every accreted system in Auriga, we compute stellar masses and metallicities two ways: considering the total system (bound + lost material) and only considering the progenitor. Accreted systems in Auriga have a tight relation between total stellar mass and metallicity, with scatter at a fixed stellar mass driven by age. When only considering the progenitor, the tidally evolved mass–metallicity relation has similar scatter (~0.27 dex) as observed for the Local Group satellites (~0.23 dex). Satellites that lie above the evolved relation have experienced substantial mass-loss and typically have low metallicity for their total stellar mass. Even satellites that fall exactly on the evolved relation can lose over half of their stellar mass. Only satellites substantially below the evolved relation are reliably intact. Based on their offset from the observed relation, we predict which Milky Way and M31 satellites have tidal tails waiting to be discovered.</p>}},
  author       = {{Riley, Alexander H. and Bieri, Rebekka and Deason, Alis J. and Shipp, Nora and Simpson, Christine M. and Fragkoudi, Francesca and Gómez, Facundo A. and Grand, Robert J.J. and Marinacci, Federico}},
  issn         = {{0035-8711}},
  keywords     = {{galaxies: evolution; galaxies: formation; Galaxy: halo; Local Group}},
  language     = {{eng}},
  number       = {{3}},
  publisher    = {{Oxford University Press}},
  series       = {{Monthly Notices of the Royal Astronomical Society}},
  title        = {{Auriga Streams III : the mass–metallicity relation does not rule out tidal mass-loss in Local Group satellites}},
  url          = {{http://dx.doi.org/10.1093/mnras/stag029}},
  doi          = {{10.1093/mnras/stag029}},
  volume       = {{546}},
  year         = {{2026}},
}