An LBT view of the co-rotating group of galaxies around NGC 2750: Deep imaging and new satellite candidates

¹ Institute of Physics, Laboratory of Astrophysics, École Polytechnique Fédérale de Lausanne (EPFL), 1290 Sauverny, Switzerland
² Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
³ Institute of Astronomy, Madingley Rd, Cambridge CB3 0HA, UK
⁴ Visiting Fellow, Clare Hall, University of Cambridge, Cambridge, UK
⁵ Astronomical Observatory, Volgina 7, 11060 Belgrade, Serbia
⁶ Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Straße 24/25, 14476 Potsdam, Germany

^⋆ Corresponding author: salvatore.taibi@epfl.ch

Received: 4 March 2025
Accepted: 20 June 2025

Abstract

Context. Some galaxies such as the Milky Way and Andromeda display coherently rotating satellite planes, posing tensions with cosmological simulations. NGC 2750 has emerged as an additional candidate system hosting a co-rotating group of galaxies.

Aims. This work aims to verify the presence of a coherent plane of satellites around NGC 2750 by identifying new candidate dwarf galaxies and low surface brightness features.

Methods. We conducted deep photometric observations of NGC 2750 and its surroundings over an area of ∼35′×30′ using the Large Binocular Telescope (LBT) in the g- and r-bands. Standard data reduction techniques were employed to improve the detection of low-surface-brightness-features down to a depth of μ_r∼31 mag arcsec⁻². We analysed the morphology of NGC 2750 and other galaxies in this system for signs of tidal interactions and performed structural and photometric analyses of recently identified candidate satellites.

Results. Our observations led to the discovery of six new candidate dwarf galaxies, one of which exhibits properties consistent with an ultra-diffuse galaxy. We identified tidal features around NGC 2750, suggesting past interactions with its neighbouring satellites. While the spatial distribution of satellites suggests a moderate flattening, and this flattening is supported by the new candidates, follow-up spectroscopic measurements of the new candidates have the potential to bolster or diminish the strong kinematic coherence observed previously. The luminosity function of NGC 2750 shows an excess of bright satellites compared to similar systems, contributing to the growing evidence of discrepancies between observed satellite distributions and predictions from cosmological simulations.