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A E Watkins, H Salo, S Kaviraj, C A Collins, J H Knapen, A Venhola, J Román, A possible signature of the influence of tidal perturbations in dwarf galaxy scaling relations, Monthly Notices of the Royal Astronomical Society, Volume 521, Issue 2, May 2023, Pages 2012–2029,

A possible signature of the influence of tidal perturbations in dwarf galaxy scaling relations

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Author: Watkins, A. E.1; Salo, H.2; Kaviraj, S.1;
Organizations: 1Centre for Astrophysics Research, School of Physics, Astronomy and Mathematics, University of Hertfordshire, Hatfield AL10 9AB, UK
2Space Physics and Astronomy Research Unit, University of Oulu, Pentti Kaiteran katu 1, FI-90014 Oulu, Finland
3Astrophysics Research Institute, Liverpool John Moores University, IC2 Building, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF, UK
4Instituto de Astrofísica de Canarias, Vía Láctea S/N, E-38205 La Laguna, Spain
5Departamento de Astrof´ısica, Universidad de La Laguna, E-38206 La Laguna, Spain
6Kapteyn Astronomical Institute, University of Groningen, PO Box 800, NL-9700 AV Groningen, the Netherlands
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 9.2 MB)
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Language: English
Published: Oxford University Press, 2023
Publish Date: 2023-10-24


Dwarf galaxies are excellent cosmological probes, because their shallow potential wells make them very sensitive to the key processes that drive galaxy evolution, including baryonic feedback, tidal interactions, and ram pressure stripping. However, some of the key parameters of dwarf galaxies, which help trace the effects of these processes, are still debated, including the relationship between their sizes and masses. We re-examine the Fornax Cluster dwarf population from the point of view of isomass-radius–stellar mass relations (IRSMRs) using the Fornax Deep Survey Dwarf galaxy Catalogue, with the centrally located (among dwarfs) \(3.63 \mathcal {M}_{\odot } \text{pc}^{-2}\) isodensity radius defining our fiducial relation. This relation is a powerful diagnostic tool for identifying dwarfs with unusual structure, as dwarf galaxies’ remarkable monotonicity in light profile shapes, as a function of stellar mass, reduces the relation’s scatter tremendously. By examining how different dwarf properties (colour, 10th nearest neighbour distance, etc.) correlate with distance from our fiducial relation, we find a significant population of structural outliers with comparatively lower central mass surface density and larger half-light-radii, residing in locally denser regions in the cluster, albeit with similar red colours. We propose that these faint, extended outliers likely formed through tidal disturbances, which make the dwarfs more diffuse, but with little mass-loss. Comparing these outliers with ultra-diffuse galaxies (UDGs), we find that the term UDG lacks discriminatory power; UDGs in the Fornax Cluster lie both on and off of IRSMRs defined at small radii, while IRSMR outliers with masses below \(\sim 10^{7.5} \mathcal {M}_{\odot }\) are excluded from the UDG classification due to their small effective radii.

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Series: Monthly notices of the Royal Astronomical Society
ISSN: 0035-8711
ISSN-E: 1365-8711
ISSN-L: 0035-8711
Volume: 521
Issue: 2
Pages: 2012 - 2029
DOI: 10.1093/mnras/stad654
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: We thank the anonymous referee for their thorough and careful assessment of the paper. SK and AW acknowledge support from the STFC [ST/S00615X/1]. SK acknowledges a Senior Research Fellowship from Worcester College, Oxford. JHK and JR acknowledge financial support from the State Research Agency (AEI-MCINN) of the Spanish Ministry of Science and Innovation under the grant 'The structure and evolution of galaxies and their central regions' with reference PID2019-105602GB-I00/10.13039/501100011033, from the ACIISI, Consejeria de Economia, Conocimiento y Empleo del Gobierno de Canarias and the European Regional Development Fund (ERDF) under grant with reference PROID2021010044, and from IAC project P/300724, financed by the Ministry of Science and Innovation, through the State Budget and by the Canary Islands Department of Economy, Knowledge and Employment, through the Regional Budget of the Autonomous Community. JR acknowledges funding from University of La Laguna through the Margarita Salas Program from the Spanish Ministry of Universities ref. UNI/551/2021-May 26, and under the EU Next Generation programme. For the purpose of open access, the author has applied a Creative Commons Attribution (CC BY) licence to any Author Accepted Manuscript version arising from this submission.
Dataset Reference: The data underlying this article are available at the Centre de Données Astronomique de Strasbourg (CDS), at 10.26093/cds/vizier.36470100 and + A/660/A69; at the NASA/IPAC Infrared Science Archive, at; and at the European Southern Observatory Science Archive Facility, at We will also make all of our isomass radii available in table format at MNRAS and at the CDS upon publication. We show an example of this table in Section C.
Copyright information: © 2023 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.