The Rogue One: a dark matter-dominated dwarf in the trail of dark matter-deficient galaxies
6 affiliations
- 1Centre for Astrophysics and Supercomputing, Swinburne University of Technology , Hawthorn, VIC 3122 ,
- 2Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas , P-4150-762 Porto ,
- 3Department of Physics and Astronomy, San José State University, One Washington Square , San Jose, CA 95192 ,
- 4Department of Astronomy and Astrophysics, University of California Santa Cruz , 1156 High Street, Santa Cruz, CA 95064 ,
- 5Department of Astronomy & Astrophysics, University of Toronto , 50 St. George Street, Toronto, ON M5S 3H4 ,
- 6International Centre for Radio Astronomy Research (ICRAR), M468, The University of Western Australia , 35 Stirling Hwy, Crawley, WA 6009 ,
Abstract
We present the first measurement of the stellar velocity dispersion of LEDA 4014647, a compact dwarf galaxy spatially aligned with the NGC 1052 trail, a linear chain of dark matter-deficient galaxies (DMDGs) proposed to have formed in a single high-speed dwarf–dwarf collision ∼ 8 Gyr ago. Using integral-field spectroscopy obtained with the Keck Cosmic Web Imager, we measure a stellar velocity dispersion of σ = 15.8 ± 2.0 km s−1 within the half-light radius (Re). We derive a dynamical mass within the 3D half-light radius of Mdyn(lt r1/2) = (1.5 ± 0.4) × 108 M⊙, a factor of ∼ 3 larger than the enclosed stellar mass, implying a dark matter (DM) fraction of fDM = 0.7 ± 0.1 at r1/2. Full-spectrum stellar population fitting yields an old (t ≈ 13 Gyr) and metal-poor ([M/H] ≈ −1.2 dex) stellar population, consistent with independent photometric estimates and predating the proposed collision epoch. LEDA 4014647 is therefore a DM-dominated system and cannot have formed from the DM-free, shock-compressed gas that produced the proposed trail DMDGs DF2, DF4, and DF9. Its nature, however, remains an open question: While a chance projection along the trail axis is a possible explanation, its old stellar population, compact morphology, and DM content are also consistent with the surviving collisionless remnant of one of the progenitor dwarfs of the dwarf–dwarf collision. Distinguishing between these two scenarios will ultimately require deeper spectroscopy to tighten the stellar population and DM halo constraints, and targeted N-body and hydrodynamical simulations tracking the post-encounter fate of the progenitors.
Related
- Dark Matter Deficient Galaxies as Probes of Dark Matter
- Probing Multi-formation Channels of Dark Matter-Deficient Galaxies in a Simulated Universe
- CROCODILE-SIDM: Tidal Formation of Dark Matter-Deficient Galaxies as a Test Case
- Using the Circumgalactic Medium of Dwarf Galaxies as a Calorimetric Dark Matter Detector
- Tidal origin of dark-matter free dwarf galaxies in the NGC 1052 group
BibTeX
@article{vaz2026rogue,
title = {{The Rogue One: a dark matter-dominated dwarf in the trail of dark matter-deficient galaxies}},
author = {Daniel Vaz and Arsen Levitskiy and Duncan Forbes and Aaron J Romanowsky and Jonah Gannon and Jean P Brodie and Yimeng Tang and Kenji Bekki and Warrick J Couch},
journal = {Monthly Notices of the Royal Astronomical Society},
year = {2026},
month = oct,
doi = {10.1093/mnras/stag1895},
url = {https://academic.oup.com/mnras/article/doi/10.1093/mnras/stag1895/8875684},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - The Rogue One: a dark matter-dominated dwarf in the trail of dark matter-deficient galaxies
AU - Daniel Vaz
AU - Arsen Levitskiy
AU - Duncan Forbes
AU - Aaron J Romanowsky
AU - Jonah Gannon
AU - Jean P Brodie
AU - Yimeng Tang
AU - Kenji Bekki
AU - Warrick J Couch
PY - 2026
DA - 2026/10/07
JO - Monthly Notices of the Royal Astronomical Society
DO - 10.1093/mnras/stag1895
UR - https://academic.oup.com/mnras/article/doi/10.1093/mnras/stag1895/8875684
AB - We present the first measurement of the stellar velocity dispersion of LEDA 4014647, a compact dwarf galaxy spatially aligned with the NGC 1052 trail, a linear chain of dark matter-deficient galaxies (DMDGs) proposed to have formed in a single high-speed dwarf–dwarf collision ∼ 8 Gyr ago. Using integral-field spectroscopy obtained with the Keck Cosmic Web Imager, we measure a stellar velocity dispersion of σ = 15.8 ± 2.0 km s^−1 within the half-light radius (R_e). We derive a dynamical mass within the 3D half-light radius of M_dyn(lt r_1/2) = (1.5 ± 0.4) × 10^8 M_⊙, a factor of ∼ 3 larger than the enclosed stellar mass, implying a dark matter (DM) fraction of f_DM = 0.7 ± 0.1 at r_1/2. Full-spectrum stellar population fitting yields an old (t ≈ 13 Gyr) and metal-poor ([M/H] ≈ −1.2 dex) stellar population, consistent with independent photometric estimates and predating the proposed collision epoch. LEDA 4014647 is therefore a DM-dominated system and cannot have formed from the DM-free, shock-compressed gas that produced the proposed trail DMDGs DF2, DF4, and DF9. Its nature, however, remains an open question: While a chance projection along the trail axis is a possible explanation, its old stellar population, compact morphology, and DM content are also consistent with the surviving collisionless remnant of one of the progenitor dwarfs of the dwarf–dwarf collision. Distinguishing between these two scenarios will ultimately require deeper spectroscopy to tighten the stellar population and DM halo constraints, and targeted N-body and hydrodynamical simulations tracking the post-encounter fate of the progenitors.
SN - 0035-8711
SN - 1365-2966
ER -