Improved constraints on the Milky Way potential using the M68 stream and DESI spectroscopic data

@article{palau2026improved,
  title = {{Improved constraints on the Milky Way potential using the M68 stream and DESI spectroscopic data}},
  author = {Carles G Palau and Wenting Wang and Jiaxin Han and J Aguilar and S Ahlen and F Beutler and D Bianchi and D Brooks and A Carnero Rosell and F J Castander and T Claybaugh and A Cuceu and A de la Macorra and J E Forero-Romero and E Gaztañaga and Satya Gontcho A Gontcho and G Gutierrez and J Guy and D Kirkby and A Kremin and M Landriau and L Le Guillou and A Leauthaud and G E Medina and A Meisner and R Miquel and S Nadathur and H E Noriega and E Paillas and N Palanque-Delabrouille and W J Percival and F Prada and I Pérez-Ràfols and C Ravoux and G Rossi and R Ruggeri and E Sanchez and C Saulder and D Schlegel and M Schubnell and M Siudek and G Tarlé and B A Weaver and H Zou},
  journal = {Monthly Notices of the Royal Astronomical Society},
  year = {2026},
  month = oct,
  doi = {10.1093/mnras/stag1971},
  url = {https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stag1971/8979789},
  note = {CC BY 4.0},
}

TY  - JOUR
TI  - Improved constraints on the Milky Way potential using the M68 stream and DESI spectroscopic data
AU  - Carles G Palau
AU  - Wenting Wang
AU  - Jiaxin Han
AU  - J Aguilar
AU  - S Ahlen
AU  - F Beutler
AU  - D Bianchi
AU  - D Brooks
AU  - A Carnero Rosell
AU  - F J Castander
AU  - T Claybaugh
AU  - A Cuceu
AU  - A de la Macorra
AU  - J E Forero-Romero
AU  - E Gaztañaga
AU  - Satya Gontcho A Gontcho
AU  - G Gutierrez
AU  - J Guy
AU  - D Kirkby
AU  - A Kremin
AU  - M Landriau
AU  - L Le Guillou
AU  - A Leauthaud
AU  - G E Medina
AU  - A Meisner
AU  - R Miquel
AU  - S Nadathur
AU  - H E Noriega
AU  - E Paillas
AU  - N Palanque-Delabrouille
AU  - W J Percival
AU  - F Prada
AU  - I Pérez-Ràfols
AU  - C Ravoux
AU  - G Rossi
AU  - R Ruggeri
AU  - E Sanchez
AU  - C Saulder
AU  - D Schlegel
AU  - M Schubnell
AU  - M Siudek
AU  - G Tarlé
AU  - B A Weaver
AU  - H Zou
PY  - 2026
DA  - 2026/10/22
JO  - Monthly Notices of the Royal Astronomical Society
DO  - 10.1093/mnras/stag1971
UR  - https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stag1971/8979789
AB  - 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_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± 0.09 kpc.
SN  - 0035-8711
SN  - 1365-2966
ER  -