DESI DR2 Results III: The Mass of the Milky Way
Abstract
We present measurements of the mass of the Milky Way using distant halo stars selected from the Dark Energy Spectroscopic Instrument (DESI) Data Release 2 (DR2). We apply four dynamical modeling methods to 10,036 RR Lyrae (RRL) and blue horizontal branch (BHB) stars with 6D phase space coordinates that span from ∼10 to 95 kpc from the Galactic center, the largest samples of their kind. All methods are applied to mock surveys based on cosmological simulations that include generating individual tracer stars, convolving their phase-space coordinates with DESI and Gaia DR3-like uncertainties, and tailored models of the survey selection functions. By comparing the performance on these mocks, we quantify how systematic biases from both methodology assumptions and galaxy disequilibrium impact each estimate. The mock-based systematics, which differ by method and tracer, are used to correct the individual estimates and to derive joint estimates using a rigorous formalism that accounts for per-method biases and residual correlations between methods. We obtain a joint estimate of the mass within 80 kpc to be M(r < 80 kpc) = 6.36+0.53−0.48 × 1011 M⊙ and a virial mass estimate of M200c = 1.19+0.14−0.12 × 1012 M⊙, with similar results when combining only RRL-based or BHB-based measurements. These results provide a roadmap for future DESI efforts, as well as those in other spectroscopic surveys, to reliably constrain the mass of our Galaxy.
Related
- Mock catalogues for the DESI DR2 Milky Way mass modeling effort
- Constraining the Milky Way Mass profile with data driven distribution function using DESI DR2 halo stars
- A distribution-function estimate of the Milky Way mass profile from outer halo stars in DESI DR2
- Star formation history of Draco revealed by DESI DR1: suppressed early star formation efficiency for Milky Way dwarf galaxies
- The Binary Fraction of Milky Way Field Stars in DESI: Dependence on Chemical Abundance
BibTeX
@misc{collaboration2026desi,
title = {{DESI DR2 Results III: The Mass of the Milky Way}},
author = {DESI Collaboration and C. Aganze and J. Aguilar and S. Ahlen and C. Allende Prieto and E. Armengaud and A. Aviles and S. Bailey and A. Bault and J. Behera and L. Beraldo e Silva and J. R. Bermejo-Climent and F. Beutler and D. Bianchi and S. Brieden and A. Brodzeller and D. Brooks and A. Byström and T. M. Callingham and R. Canning and A. Carnero Rosell and F. J. Castander and E. Chaussidon and J. Chaves-Montero and X. Chen and Yingtian Chen and A. P. Cooper and A. Cuceu and Tamara M. Davis and K. S. Dawson and A. de la Macorra and J. Della Costa and Arjun Dey and Biprateep Dey and Z. Ding and P. Doel and G. M. Eadie and H. Ebina and V. A. Fawcett and S. Ferraro and A. Font-Ribera and J. E. Forero-Romero and C. S. Frenk and C. Garcia Palau and E. Gaztañaga and Oleg Y. Gnedin and Satya Gontcho A Gontcho and A. X. Gonzalez-Morales and G. Gutierrez and J. Guy and Jiaxin Han and H. K. Herrera-Alcantar and C. Holm-Hansen and K. Honscheid and D. Huterer and M. Ishak and S. Juneau and T. Karim and S. Kent and D. Kirkby},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.05518},
eprint = {2611.05518},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.05518},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - DESI DR2 Results III: The Mass of the Milky Way
AU - DESI Collaboration
AU - C. Aganze
AU - J. Aguilar
AU - S. Ahlen
AU - C. Allende Prieto
AU - E. Armengaud
AU - A. Aviles
AU - S. Bailey
AU - A. Bault
AU - J. Behera
AU - L. Beraldo e Silva
AU - J. R. Bermejo-Climent
AU - F. Beutler
AU - D. Bianchi
AU - S. Brieden
AU - A. Brodzeller
AU - D. Brooks
AU - A. Byström
AU - T. M. Callingham
AU - R. Canning
AU - A. Carnero Rosell
AU - F. J. Castander
AU - E. Chaussidon
AU - J. Chaves-Montero
AU - X. Chen
AU - Yingtian Chen
AU - A. P. Cooper
AU - A. Cuceu
AU - Tamara M. Davis
AU - K. S. Dawson
AU - A. de la Macorra
AU - J. Della Costa
AU - Arjun Dey
AU - Biprateep Dey
AU - Z. Ding
AU - P. Doel
AU - G. M. Eadie
AU - H. Ebina
AU - V. A. Fawcett
AU - S. Ferraro
AU - A. Font-Ribera
AU - J. E. Forero-Romero
AU - C. S. Frenk
AU - C. Garcia Palau
AU - E. Gaztañaga
AU - Oleg Y. Gnedin
AU - Satya Gontcho A Gontcho
AU - A. X. Gonzalez-Morales
AU - G. Gutierrez
AU - J. Guy
AU - Jiaxin Han
AU - H. K. Herrera-Alcantar
AU - C. Holm-Hansen
AU - K. Honscheid
AU - D. Huterer
AU - M. Ishak
AU - S. Juneau
AU - T. Karim
AU - S. Kent
AU - D. Kirkby
PY - 2026
DA - 2026/11/03
PB - arXiv
DO - 10.48550/arxiv.2611.05518
UR - https://arxiv.org/abs/2611.05518
AB - We present measurements of the mass of the Milky Way using distant halo stars selected from the Dark Energy Spectroscopic Instrument (DESI) Data Release 2 (DR2). We apply four dynamical modeling methods to 10,036 RR Lyrae (RRL) and blue horizontal branch (BHB) stars with 6D phase space coordinates that span from ∼10 to 95 kpc from the Galactic center, the largest samples of their kind. All methods are applied to mock surveys based on cosmological simulations that include generating individual tracer stars, convolving their phase-space coordinates with DESI and Gaia DR3-like uncertainties, and tailored models of the survey selection functions. By comparing the performance on these mocks, we quantify how systematic biases from both methodology assumptions and galaxy disequilibrium impact each estimate. The mock-based systematics, which differ by method and tracer, are used to correct the individual estimates and to derive joint estimates using a rigorous formalism that accounts for per-method biases and residual correlations between methods. We obtain a joint estimate of the mass within 80 kpc to be M(r < 80 kpc) = 6.36^+0.53_−0.48 × 10^11 M_⊙ and a virial mass estimate of M_200c = 1.19^+0.14_−0.12 × 10^12 M_⊙, with similar results when combining only RRL-based or BHB-based measurements. These results provide a roadmap for future DESI efforts, as well as those in other spectroscopic surveys, to reliably constrain the mass of our Galaxy.
ER -