Formation mechanism of dark matter-deficient galaxies

Determine the physical formation mechanism or mechanisms responsible for dark matter-deficient galaxies, including whether tidal stripping, baryonic processes, dark-matter self-interactions, or alternative scenarios dominate their origin.

Background

Dark matter-deficient galaxies exhibit unusually low dynamical masses relative to their stellar masses, challenging conventional abundance-matching expectations. The paper notes that several formation scenarios have been proposed, including high-speed dwarf-galaxy collisions and tidal stripping by a massive host galaxy.

Although the paper investigates how self-interacting dark matter and dynamical friction affect the tidal formation of such systems, it does not resolve the broader question of which physical mechanism explains the observed population of dark matter-deficient galaxies.

References

First, we retain the illustrative progenitor value \mu_i=100 used in our previous analysis, although the actual progenitor ratio of TTT J1237327+143535 is not known.

— Dark Matter-Baryon Separability Predicts the Dynamics of an Almost-Dark Galaxy  (2609.10661 - Trivedi et al., 9 Sep 2026) in Paragraph beginning “While it is now apparent that our condition can indeed be consistent with the observations of almost-dark galaxies”

Together, these results indicate that the SIDM solution for UDG-1, while statistically viable, is not physically robust. However, this shortcoming stems from the limited quality and radial coverage of the available data, and the model cannot be completely excluded, thus warranting further investigation as more extended kinematic data become available.

— Probing dynamics of extreme galaxies I. Dark matter content in ultra-diffuse galaxies  (2609.10700 - Bouchè et al., 9 Sep 2026) in Section 5.3, subsection “Self-interacting dark matter”

Since then, additional DMDG candidates have been identified \citep{Guo_2020_furtherDMDGs}, making the formation mechanism of such galaxies an important open problem in galaxy formation theory.

— CROCODILE-SIDM: Tidal Formation of Dark Matter-Deficient Galaxies as a Test Case  (2609.09729 - Kihara et al., 9 Sep 2026) in Section 1, Introduction

A quantitative treatment would require applying the same mass estimator to the mock kinematics, and ultimately a cosmological sample in which the orbits, viewing angles, and assembly histories are not controlled by hand, which we leave to future work.

— CROCODILE-SIDM: Tidal Formation of Dark Matter-Deficient Galaxies as a Test Case  (2609.09729 - Kihara et al., 9 Sep 2026) in Section 3.2, “Mock-observed Mass Ratio”