{
  "abstract": "We present a selection of stars belonging to the stellar stream of the M68 (NGC 4590) globular cluster, also known as Fjörm. This star selection is an improvement on previous ones that used only Gaia data, as it incorporates spectroscopic measurements from the DESI survey and photometric data from the DESI Legacy Surveys. The selection contains 96 stars, each with five phase-space parameters from Gaia-DR3 and radial velocity from DESI, covering the entire observed section of the stream. This constitutes the largest selection of M68 stream stars with measured radial velocities to date. The observed stream is wider than expected from N-body simulations, and the stars farthest from the centre of the stream appear to be correlated in radial velocity space. This suggests that these stars cannot have been stripped from the cluster in a static axisymmetric potential. By modelling a mock sample of stream stars created using an N-body simulation, we found that we could reliably constrain the disc mass Md and the dark matter halo axis ratio qh of the Milky Way. This is because the stream flows close to and almost parallel to the disc. Using the 44 stars that are consistent with having been stripped from the cluster, combined with measurements of the Milky Way’s rotation curve, we constrain the Galactic potential, obtaining Md = 5.34 ± 0.57 × 1010 M⊙ and an oblate halo of $q_{\\rm h} = 0.83^{+0.06}_{-0.05}$. Additionally, by fitting the stream track, we estimate the Heliocentric distance of M68 to be $r_H^{M68}=10.55\\pm 0.09$ kpc.",
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  "affiliations": [
    "Shanghai Jiao Tong University Department of Astronomy, , 800 Dongchuan Road, Shanghai 200240 ,",
    "Shanghai Key Laboratory for Particle Physics and Cosmology , 800 Dongchuan Road, Shanghai 200240 ,",
    "Lawrence Berkeley National Laboratory , 1 Cyclotron Road, Berkeley, CA 94720 ,",
    "Boston University, 590 Commonwealth Avenue Department of Physics, , Boston, MA 02215",
    "Institute for Astronomy, University of Edinburgh , Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ ,",
    "Università degli Studi di Milano Dipartimento di Fisica “Aldo Pontremoli”, , Via Celoria 16, I-20133 Milano ,",
    "INAF-Osservatorio Astronomico di Brera , Via Brera 28, 20122 Milano ,",
    "University College London Department of Physics & Astronomy, , Gower Street, London, WC1E 6BT ,",
    "Universidad de La Laguna (ULL) Departamento de Astrofísica, , E-38206, La Laguna, Tenerife ,",
    "Instituto de Astrofísica de Canarias , Vía Láctea, s/n, E-38205 La Laguna, Tenerife ,",
    "Institut d’Estudis Espacials de Catalunya (IEEC) , Esteve Terradas 1, Edifici RDIT, Campus PMT-UPC, 08860 Castelldefels ,",
    "Institute of Space Sciences, ICE-CSIC , Campus UAB, Carrer de Can Magrans s/n, 08913 Bellaterra, Barcelona ,",
    "Instituto de Física, Universidad Nacional Autónoma de México, Circuito de la Investigación Científica , Ciudad Universitaria, Cd. de México C. P. 04510 ,",
    "Universidad de los Andes Departamento de Física, , Cra. 1 No. 18A-10, Edificio Ip, CP 111711, Bogotá ,",
    "Observatorio Astronómico, Universidad de los Andes , Cra. 1 No. 18A-10, Edificio H, CP 111711 Bogotá ,",
    "Institute of Cosmology and Gravitation, University of Portsmouth , Dennis Sciama Building, Portsmouth, PO1 3FX ,",
    "University of Virginia , Department of Astronomy, Charlottesville, VA 22904 ,",
    "Fermi National Accelerator Laboratory , PO Box 500, Batavia, IL 60510 ,",
    "University of California Department of Physics and Astronomy, , Irvine, 92697 ,",
    "Sorbonne Université, CNRS/IN2P3, Laboratoire de Physique Nucléaire et de Hautes Energies (LPNHE) , FR-75005 Paris ,",
    "UCO/Lick Observatory Department of Astronomy and Astrophysics, , University of California, 1156 High Street, Santa Cruz, CA 95064 ,",
    "University of California Department of Astronomy and Astrophysics, , Santa Cruz, 1156 High Street, Santa Cruz, CA 95065 ,",
    "University of Toronto Department of Astronomy & Astrophysics, , Toronto, ON M5S 3H4 ,",
    "NSF NOIRLab , 950 N. Cherry Ave., Tucson, AZ 85719 ,",
    "Institució Catalana de Recerca i Estudis Avançats , Passeig de Lluís Companys, 23, 08010 Barcelona ,",
    "Institut de Física d’Altes Energies (IFAE), The Barcelona Institute of Science and Technology , Edifici Cn, Campus UAB, 08193, Bellaterra (Barcelona) ,",
    "Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México , Av. Universidad s/n, Cuernavaca, Morelos, C. P. 62210 ,",
    "Instituto de Estudios Astrofísicos, Facultad de Ingeniería y Ciencias, Universidad Diego Portales , Av. Ejército Libertador 441, Santiago ,",
    "Steward Observatory, University of Arizona , 933 N. Cherry Avenue, Tucson, AZ 85721 ,",
    "IRFU, CEA, Université Paris-Saclay , F-91191 Gif-sur-Yvette ,",
    "University of Waterloo Department of Physics and Astronomy, , 200 University Ave W, Waterloo, ON N2L 3G1 ,",
    "Perimeter Institute for Theoretical Physics , 31 Caroline St. North, Waterloo, ON N2L 2Y5 ,",
    "Waterloo Centre for Astrophysics, University of Waterloo , 200 University Ave W, Waterloo, ON N2L 3G1 ,",
    "Instituto de Astrofísica de Andalucía (CSIC) , Glorieta de la Astronomía, s/n, E-18008 Granada ,",
    "Universitat Politècnica de Catalunya Departament de Física, EEBE, , c/Eduard Maristany 10, 08930 Barcelona ,",
    "Université Clermont-Auvergne , CNRS, LPCA, 63000 Clermont-Ferrand ,",
    "Sejong University Department of Physics and Astronomy, , 209 Neungdong-ro, Gwangjin-gu, Seoul 05006 ,",
    "Queensland University of Technology, School of Chemistry & Physics , George St, Brisbane 4001 ,",
    "CIEMAT , Avenida Complutense 40, E-28040 Madrid ,",
    "Max Planck Institute for Extraterrestrial Physics , Gießenbachstraße 1, 85748 Garching ,"
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  "bibtex": "https://research.draconitic.com/paper/8ghf053tkx0xt.bib",
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  "doi": "10.1093/mnras/stag1971",
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  "issns": [
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    "1365-2966"
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  "licence_label": "CC BY 4.0",
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  "published": "2026-10-22",
  "publisher": "Oxford University Press (OUP)",
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  "title": "Improved constraints on the Milky Way potential using the M68 stream and DESI spectroscopic data",
  "title_text": "Improved constraints on the Milky Way potential using the M68 stream and DESI spectroscopic data",
  "type": "peer-reviewed",
  "updated_at": "2026-10-30T12:18:17Z",
  "url": "https://research.draconitic.com/paper/8ghf053tkx0xt",
  "venue": "Monthly Notices of the Royal Astronomical Society",
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