University of Oulu

Elena Asencio, Indranil Banik, Steffen Mieske, Aku Venhola, Pavel Kroupa, Hongsheng Zhao, The distribution and morphologies of Fornax Cluster dwarf galaxies suggest they lack dark matter, Monthly Notices of the Royal Astronomical Society, Volume 515, Issue 2, September 2022, Pages 2981–3013,

The distribution and morphologies of Fornax Cluster dwarf galaxies suggest they lack dark matter

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Author: Asencio, Elena1; Banik, Indranil2; Mieske, Steffen3;
Organizations: 1Helmholtz-Institut für Strahlen und Kernphysik (HISKP), University of Bonn, Nussallee 14 − 16, D-53115 Bonn, Germany
2Scottish Universities Physics Alliance, University of Saint Andrews, North Haugh, Saint Andrews, Fife KY16 9SS, UK
3European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile
4Space Physics and Astronomy Research Unit, University of Oulu, Pentti Kaiteran Katu 1, FI-90014 Oulu, Finland
5Astronomical Institute, Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, CZ-180 00 Praha 8, Czech Republic
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Version: published version
Access: open
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Language: English
Published: Oxford University Press, 2022
Publish Date: 2022-09-06


Due to their low surface brightness, dwarf galaxies are particularly susceptible to tidal forces. The expected degree of disturbance depends on the assumed gravity law and whether they have a dominant dark halo. This makes dwarf galaxies useful for testing different gravity models. In this project, we use the Fornax Deep Survey (FDS) dwarf galaxy catalogue to compare the properties of dwarf galaxies in the Fornax Cluster with those predicted by the Lambda cold dark matter (ΛCDM) standard model of cosmology and Milgromian dynamics (MOND). We construct a test particle simulation of the Fornax system. We then use the Markov Chain Monte Carlo (MCMC) method to fit this to the FDS distribution of tidal susceptibility η (half-mass radius divided by theoretical tidal radius), the fraction of dwarfs that visually appear disturbed as a function of η, and the distribution of projected separation from the cluster centre. This allows us to constrain the η value at which dwarfs should get destroyed by tides. Accounting for an r′-band surface brightness limit of 27.8 magnitudes per square arcsec, the required stability threshold is ηdestr=0.25+0.07−0.03 in ΛCDM and 1.88+0.85−0.53 in MOND. The ΛCDM value is in tension with previous N-body dwarf galaxy simulations, which indicate that ηdestr ≈ 1. Our MOND N-body simulations indicate that ηdestr = 1.70 ± 0.30, which agrees well with our MCMC analysis of the FDS. We therefore conclude that the observed deformations of dwarf galaxies in the Fornax Cluster and the lack of low surface brightness dwarfs towards its centre are incompatible with ΛCDM expectations but well consistent with MOND.

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Series: Monthly notices of the Royal Astronomical Society
ISSN: 0035-8711
ISSN-E: 1365-8711
ISSN-L: 0035-8711
Volume: 515
Issue: 2
Pages: 2981 - 3013
DOI: 10.1093/mnras/stac1765
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: EA is supported by a stipend from the Stellar Populations and Dynamics Research Group at the University of Bonn. IB is supported by Science and Technology Facilities Council grant ST/V000861/1, which also partially supports HZ. IB acknowledges support from a ‘Pathways to Research’ fellowship from the University of Bonn. PK acknowledges support through the Deutscher Akademischer Austauschdienst-Eastern European Exchange Programme.
Copyright information: © 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (