2026A&A...707L...1S

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.