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No need for dark matter: resolved kinematics of the ultra-diffuse galaxy AGC 114905

Mancera Piña, Pavel E; Fraternali, Filippo; Oosterloo, Tom; Adams, Elizabeth AK; Oman, Kyle A; Leisman, Lukas

No need for dark matter: resolved kinematics of the ultra-diffuse galaxy AGC 114905 Thumbnail


Pavel E Mancera Piña

Filippo Fraternali

Tom Oosterloo

Elizabeth AK Adams

Lukas Leisman


We present new H I interferometric observations of the gas-rich ultra-diffuse galaxy AGC 114905, which previous work, based on low-resolution data, identified as an outlier of the baryonic Tully–Fisher relation. The new observations, at a spatial resolution ∼2.5 times higher than before, reveal a regular H I disc rotating at about 23 km s−1. Our kinematic parameters, recovered with a robust 3D kinematic modelling fitting technique, show that the flat part of the rotation curve is reached. Intriguingly, the rotation curve can be explained almost entirely by the baryonic mass distribution alone. We show that a standard cold dark matter halo that follows the concentration–halo mass relation fails to reproduce the amplitude of the rotation curve by a large margin. Only a halo with an extremely (and arguably unfeasible) low concentration reaches agreement with the data. We also find that the rotation curve of AGC 114905 deviates strongly from the predictions of modified Newtonian dynamics. The inclination of the galaxy, which is measured independently from our modelling, remains the largest uncertainty in our analysis, but the associated errors are not large enough to reconcile the galaxy with the expectations of cold dark matter or modified Newtonian dynamics.


Mancera Piña, P. E., Fraternali, F., Oosterloo, T., Adams, E. A., Oman, K. A., & Leisman, L. (2022). No need for dark matter: resolved kinematics of the ultra-diffuse galaxy AGC 114905. Monthly Notices of the Royal Astronomical Society, 512(3), 3230-3242.

Journal Article Type Article
Acceptance Date Nov 28, 2021
Online Publication Date Dec 14, 2021
Publication Date 2022-05
Deposit Date Jun 16, 2022
Publicly Available Date Jun 16, 2022
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 512
Issue 3
Pages 3230-3242


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Copyright Statement
© 2021 The Author(s).<br /> Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative<br /> Commons Attribution License (, which permits unrestricted reuse, distribution, and reproduction in any medium,<br /> provided the original work is properly cited.

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