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Riley, AH, Bieri, R, Deason, AJ, Shipp, N, Simpson, CM, Fragkoudi, F, Gómez, FA, Grand, R 
ORCID: 0000-0001-9667-1340 and Marinacci, F
(2026)
Auriga Streams III: the mass–metallicity relation does not rule out tidal mass-loss in Local Group satellites.
Monthly Notices of the Royal Astronomical Society, 546 (3).
pp. 1-8.
ISSN 0035-8711
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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 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.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | 0201 Astronomical and Space Sciences; Astronomy & Astrophysics; 5101 Astronomical sciences; 5107 Particle and high energy physics; 5109 Space sciences |
| Subjects: | Q Science > QB Astronomy Q Science > QC Physics |
| Divisions: | Astrophysics Research Institute |
| Publisher: | Oxford University Press |
| Date of acceptance: | 16 December 2025 |
| Date of first compliant Open Access: | 27 February 2026 |
| Date Deposited: | 27 Feb 2026 14:11 |
| Last Modified: | 27 Feb 2026 14:11 |
| DOI or ID number: | 10.1093/mnras/stag029 |
| URI: | https://researchonline.ljmu.ac.uk/id/eprint/28156 |
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