Dwarf galaxies in the MATLAS survey: The satellite system of NGC 474 under scrutiny with MUSE

¹ Institute of Physics, Laboratory of Astrophysics, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1290 Sauverny, Switzerland
² Institut für Astro- und Teilchenphysik, Universität Innsbruck, Technikerstraße 25/8, Innsbruck A-6020, Austria
³ Observatoire Astronomique de Strasbourg (ObAS), Université de Strasbourg – CNRS, UMR 7550, Strasbourg, France
⁴ Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam, Germany
⁵ Space Physics and Astronomy Research Unit, University of Oulu, PO Box 3000 FI-90014 Oulu, Finland
⁶ INAF – Astronomical Observatory of Abruzzo, Via Maggini, 64100 Teramo, Italy
⁷ Institute of Astronomy, Madingley Rd, Cambridge CB3 0HA, UK
⁸ Departamento de Física, Universidad Técnica Federico Santa María, Santiago, Chile
⁹ Youngstown State University, One University Plaza, Youngstown, OH 44555, USA
¹⁰ European Southern Observatory, Karl-Schwarzschild Straße 2, D-85748 Garching bei München, Germany
¹¹ UK Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
¹² Department of Astronomy and Center for Galaxy Evolution Research, Yonsei University, Seoul 03722, South Korea

^⋆ Corresponding author; oliver.muller@epfl.ch

Received: 27 March 2024
Accepted: 11 November 2024

Abstract

A recent study of the distribution of dwarf galaxies in the MATLAS sample in galaxy groups revealed an excess of flattened satellite structures, reminiscent of the co-rotating planes of dwarf galaxies discovered in the local Universe. If confirmed, this lends credence to the plane-of-satellite problem and further challenges the standard model of hierarchical structure formation. However, with only photometric data and no confirmation of the satellite membership, the study could not address the plane-of-satellite problem in full detail. Here we present spectroscopic follow-up observations of one of the most promising planes-of-satellite candidates in the MATLAS survey, the satellite system of NGC 474. Employing MUSE at the VLT and full spectrum fitting, we studied 13 dwarf galaxy candidates and confirmed nine to be members of the field around NGC 474. Measuring the stellar populations of all observed galaxies, we find that the MATLAS dwarfs have lower metallicities than the Local Group dwarfs at a given luminosity. Two dwarf galaxies may form a pair of satellites based on their close projection and common velocity. Within the virial radius, we do not find a significant plane-of-satellites, however, there is a sub-population of six dwarf galaxies which seem to be anti-correlated in phase-space. Due to the low number of dwarf galaxies, this signal may arise by chance. With over 2000 dwarf galaxy candidates found in the MATLAS survey, this remains an intriguing data set to study the plane-of-satellites problem in a statistical fashion once more follow-up observations have been conducted.