The ALMA survey to Resolve exoKuiper belt Substructures (ARKS)

VI. Asymmetries and offsets

¹ Center for Astrophysics | Harvard & Smithsonian, 60 Garden St, Cambridge, MA 02138, USA
² National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475, USA
³ Joint ALMA Observatory, Avenida Alonso de Córdova 3107, Vitacura 7630355, Santiago, Chile
⁴ Millennium Nucleus on Young Exoplanets and their Moons (YEMS), Chile
⁵ Malaghan Institute of Medical Research, Gate 7, Victoria University, Kelburn Parade, Wellington, New Zealand
⁶ Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
⁷ Department of Physics and Astronomy, University of Exeter, Stocker Road, Exeter EX4 4QL, UK
⁸ European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
⁹ Department of Astronomy, Van Vleck Observatory, Wesleyan University, 96 Foss Hill Dr., Middletown, CT, 06459, USA
¹⁰ Herzberg Astronomy & Astrophysics, National Research Council of Canada, 5071 West Saanich Road, Victoria, BC V9E 2E9, Canada
¹¹ Department of Physics & Astronomy, University of Victoria, 3800 Finnerty Rd, Victoria, BC V8P 5C2, Canada
¹² Department of Astronomy and Steward Observatory, The University of Arizona, 933 North Cherry Ave, Tucson, AZ 85721, USA
¹³ UK Astronomy Technology Centre, Royal Observatory Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK
¹⁴ Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
¹⁵ School of Physics, Trinity College Dublin, the University of Dublin, College Green, Dublin 2, Ireland
¹⁶ Instituto de Astrofísica de Canarias, Vía Láctea S/N, La Laguna, 38200 Tenerife, Spain
¹⁷ Departamento de Astrofísica, Universidad de La Laguna, La Laguna, 38200 Tenerife, Spain
¹⁸ National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan
¹⁹ Department of Astronomy, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan
²⁰ Department of Astronomy, University of California, Berkeley, Berkeley, CA 94720-3411, USA
²¹ Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125, USA
²² Max-Planck-Insitut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
²³ Astrophysikalisches Institut und Universitätssternwarte, Friedrich-Schiller-Universität Jena, Schillergäßchen 2-3, 07745 Jena, Germany
²⁴ Academia Sinica Institute of Astronomy and Astrophysics, 11F of AS/NTU Astronomy-Mathematics Building, No.1, Sect. 4, Roosevelt Rd, Taipei 106319, Taiwan.
²⁵ Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences, MTA Centre of Excellence, Konkoly-Thege Miklós út 15–17, 1121 Budapest, Hungary
²⁶ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
²⁷ Large Binocular Telescope Observatory, The University of Arizona, 933 North Cherry Ave, Tucson, AZ 85721, USA
²⁸ Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia
²⁹ Institute of Physics and Astronomy, ELTE Eötvös Loránd University, Pázmány Péter sétány 1/A, 1117 Budapest, Hungary
³⁰ Department of Physics and Astronomy, Johns Hopkins University, 3400 N Charles Street, Baltimore, MD 21218, USA
³¹ Departamento de Física, Universidad de Santiago de Chile, Av. Víctor Jara 3493, Santiago, Chile
³² Center for Interdisciplinary Research in Astrophysics Space Exploration (CIRAS), Universidad de Santiago, Santiago, Chile

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

Received: 23 July 2025
Accepted: 13 November 2025

Abstract

Context. Asymmetries in debris discs provide unique clues to understand the evolution and architecture of planetary systems. Previous studies of debris discs at (sub)millimetre wavelengths have suggested the presence of asymmetries in a wide variety of systems, yet the lack of sufficiently sensitive high-resolution observations means that the typical properties of debris disc asymmetries have not been studied at the population level. The aim of the ALMA survey to Resolve exoKuiper belt Substructures (ARKS) is to expand our understanding of radial and vertical dust structures, as well as gas distributions and kinematics, in debris discs. The ARKS sample of 24 highly resolved targets in ALMA’s Bands 6 and 7 (1.1–1.4 mm and 0.8–1.1 mm, respectively) provided a unique opportunity to study their asymmetries.

Aims. Here, in ARKS VI, we present a systematic analysis of the asymmetries and stellocentric offsets present in the ALMA continuum data for the ARKS survey. Our aims are to (i) identify asymmetries in debris disc dust distributions, (ii) quantify debris disc asymmetry properties, and (iii) discuss the potential origins of debris disc asymmetries. This work is the first systematic analysis of asymmetries in a large sample of well-resolved discs at (sub)millimetre wavelengths.

Methods. We utilised empirical methods to identify emission asymmetries (relative to disc major and minor axes, and azimuthal disc locations) and the presence of offset emission between disc centres and the locations of the host stars, via an analysis of their calibration procedures and disc properties. We associated observational asymmetry types (offset, major and/or minor axis, azimuthal) and plausible physical classes (arcs, eccentricities, and possible clumps and warps) associated with each source.

Results. We show that there are ten systems, almost half of the ARKS sample, that host either a continuum emission asymmetry or offset emission. Three systems host offsets (HD 15115, HD 32297, and HD 109573 (HR 4796)), four host azimuthal asymmetries (HD 9672 (49 Ceti), HD 92945, HD 107146, and HD 121617), two host an asymmetry in their major axis (HD 10647 (q¹ Eri), and HD 39060 (β Pic)), and one hosts an asymmetry in their minor axis (HD 61005). We attribute the offset asymmetries to non-zero eccentricities, and three of the azimuthal asymmetries to arcs. The presence of an asymmetry or offset in the ARKS sample appears to be correlated with the fractional luminosity of cold dust. We tentatively suggest that continuum asymmetries are more prevalent in CO-rich debris discs, suggesting that gas interactions may drive debris dust asymmetries. We identify seven other tentative asymmetries, including four in distinct ARKS systems and three in systems with otherwise significant asymmetries.

Conclusions. This study demonstrates that debris disc asymmetries in the ARKS sample are common, and plausibly so in the wider population of debris discs at (sub)-millimetre wavelengths. This means that (sub)-millimetre asymmetries plausibly await discovery in debris discs as we probe these with higher sensitivity and resolution. Throughout, we highlight future studies to further investigate the origins of debris disc asymmetries, and build on the work presented here.