Stellar tidal streams around nearby spiral galaxies with deep imaging from amateur telescopes

¹ Centro de Estudios de Física del Cosmos de Aragón (CEFCA), Unidad Asociada al CSIC, Plaza San Juan 1, 44001 Teruel, Spain
² ARAID Foundation, Avda. de Ranillas, 1-D, E-50018 Zaragoza, Spain
³ Instituto de Astrofísica de Andalucía, CSIC, Glorieta de la Astronomía, E-18080 Granada, Spain
⁴ Ruhr University Bochum, Faculty of Physics and Astronomy, Astronomical Institute (AIRUB), 44780 Bochum, Germany
⁵ Department of Physics, University of Surrey, Guildford GU2 7XH, UK, Departamento de Física de la Tierra y Astrofísica, Universidad Complutense de Madrid, E-28040 Madrid, Spain
⁶ Instituto de Física de Partículas y del Cosmos (IPARCOS), Universidad Complutense de Madrid, E-28040 Madrid, Spain
⁷ UAI – Unione Astrofili Italiani /P.I. Sezione Nazionale di Ricerca Profondo Cielo, 72024 Oria, Italy
⁸ Lund Observatory, Division of Astrophysics, Department of Physics, Lund University, Box 43 SE-221 00 Lund, Sweden
⁹ Max-Planck Institute for AstronomyKönigstuhl 17 69117 Heidelberg Germany
¹⁰ Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12–14, D-69120 Heidelberg, Germany
¹¹ Université de Strasbourg, CNRS, Observatoire astronomique de Strasbourg (ObAS), UMR 7550, F-67000 Strasbourg, France
¹² Left Hand Observatory, Boulder, CO, USA
¹³ Argelander Institut für Astronomie der Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
¹⁴ Xinjiang Astronomical Observatory, Chinese Academy of Sciences, 830011 Urumqi, Xinjiang, PR China
¹⁵ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
¹⁶ Steward Observatory, Department of Astronomy, University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85748, USA
¹⁷ Doc Greiner Research Observatory-Rancho Hidalgo, Animas, New Mexico, USA
¹⁸ CHART32, Cerro Tololo Inter-American Observatory (CTIO), Vicuña, Chile
¹⁹ Remote Observatories Southern Alpes, Verclause, France
²⁰ Black Bird Observatory II, Alder Springs, California, USA
²¹ Asociación Astronómica AstroHenares, 28823 Coslada, Madrid, Spain
²² Rancho del Sol Observatory, Camino, California, USA
²³ Tivoli Southern Sky Guest Farm, xxxx, Namibia
²⁴ MJ Observatory, Cuenca, Spain
²⁵ Universidad Internacional de Valencia (VIU), C. del Pintor Sorolla 21, 46002 Valencia, Spain
²⁶ Leiden Observatory, Leiden University, P.O. Box 9513 2300 RA Leiden, The Netherlands

^⋆⋆ Corresponding author.

Received: 1 April 2025
Accepted: 25 June 2025

Abstract

Context. Tidal interactions between massive galaxies and their satellites are fundamental processes in a universe with a Λ cold dark matter (ΛCDM) cosmology, and they redistribute material into faint features that preserve records of past galactic interactions. While stellar streams in the Local Group impressively demonstrate satellite disruption, they do not constitute a statistically significant sample. Constructing a substantial catalog of stellar streams beyond the Local Group remains challenging due to the difficulties in obtaining sufficiently deep wide-field images of galaxies. Despite their potential to illuminate dark matter distribution and galaxy formation processes overall, stellar streams remain underutilized as cosmological probes.

Aims. The Stellar Tidal Stream Survey (STSS) addresses this observational gap by leveraging amateur telescopes to obtain deep scientific-grade images of galactic outskirts capable of building a more statistically meaningful sample of stellar streams.

Methods. Over the past decade, the STSS has acquired deep (up to surface brightness limit ∼28.3 mag/arcsec² in the r-band) wide-field images of 16 nearby Milky Way analog galaxies using a coordinated network of robotic amateur telescopes, which enabled the survey to avoid the issues associated with “mosaicking” smaller images taken with a single professional telescope.

Results. Our survey revealed a diverse range of previously unreported faint features related to dwarf satellite accretion, including stellar streams, shells, and umbrella-like structures. We serendipitously discovered an ultra-diffuse galaxy (NGC150-UDG1) that shows hints of tidal tails.

Conclusions. The STSS demonstrates the suitability of modern amateur telescopes to detect and study faint, diffuse structures in large fields around nearby spiral galaxies. Their economic and accessibility advantages enable larger statistical samples with deep imaging, which are essential for testing galaxy formation models and constraining the frequency and properties of minor merger events in the local Universe.