Letter to the Editor

Stellar streams around dwarf galaxies in the local Universe

¹ Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía E-18080 Granada, Spain
² Centro de Estudios de Física del Cosmos de Aragón (CEFCA), Unidad Asociada al CSIC Plaza San Juan 1 44001 Teruel, Spain
³ ARAID Foundation, Avda. de Ranillas 1-D E-50018 Zaragoza, Spain
⁴ Niels Bohr International Academy & DARK, Niels Bohr Institute, University of Copenhagen Blegdamsvej 17 2100 Copenhagen, Denmark
⁵ Facultad de Físicas, Universidad de Sevilla, Avda. Reina Mercedes s/n Campus Reina Mercedes E-41012 Seville, Spain
⁶ CIERA and Department of Physics and Astronomy, Northwestern University 1800 Sherman Ave Evanston IL 60201, USA
⁷ NSF–Simons AI Institute for the Sky (SkAI) 172 E. Chestnut St. Chicago IL 60611, USA
⁸ UAI – Unione Astrofili Italiani/P.I. Sezione Nazionale di Ricerca Profondo Cielo 72024 Oria, Italy
⁹ Institute for Computational Cosmology, Department of Physics, Durham University South Road Durham DH1 3LE, UK
¹⁰ Department of Physics, University of Surrey Guildford GU2 7XH, UK

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 28 November 2025
Accepted: 30 January 2026

Abstract

Context. While mergers between massive galaxies and their dwarf satellites have been well studied, the properties of dwarf–dwarf satellite mergers are not well constrained. Stellar streams trace satellite disruption and, in the dwarf galaxy regime, are predicted to provide novel constraints on low-mass galaxy evolution and dark matter. However, the mass ratios required to form these streams make them challenging to detect.

Aims. We present a preview of the Stellar Stream Legacy Survey (SSLS) in the dwarf galaxy regime. The SSLS aims to produce a statistically large, homogeneous sample of stellar streams for comparison with galaxy evolution theory.

Methods. We visually inspected dwarf galaxies using the DESI Legacy Imaging Survey (DES and DECaLS footprints, r-band ∼ 29 mag arcsec⁻²) within 4–35 Mpc. We developed a classification metric to categorise accretion debris around dwarf galaxies, and measured the frequency of accretion features in the DES footprint only.

Results. We present the first release of accretion features around dwarf galaxies collected from the DES and DECaLS footprints, including 1 stream, 11 shells, and 8 asymmetric stellar halos, of which 17 constitute new identifications. In the DES footprint, we inspected 730 dwarfs and found that 5.1% (37/730) show accretion features. Although this frequency measurement is lower than the SSLS result for massive galaxies, we discuss the observational biases behind detecting streams in the dwarf galaxy regime.

Conclusions. Our results highlight the difficulty of detecting streams around dwarfs, and identify the need for improved theoretical modelling of low-mass merger morphologies. Nevertheless, they place constraints on hierarchical mass assembly in this regime.