PIRSA:26050064 Scientific Series Cosmology

DOI10.48660/26050064

Series: Cosmology and Gravitation

Majumdar, S. (2026). Mapping the Milky Way in Six Dimensions and its Rotation Curve up to the edge of the halo. Perimeter Institute. https://pirsa.org/26050064

Majumdar, Subha. Mapping the Milky Way in Six Dimensions and its Rotation Curve up to the edge of the halo. Perimeter Institute, May. 26, 2026, https://pirsa.org/26050064 

@misc{ pirsa_PIRSA:26050064,
  doi = {10.48660/26050064},
  url = {https://pirsa.org/26050064},
  author = {Majumdar, Subha},
  keywords = {Cosmology},
  language = {en},
  title = {Mapping the Milky Way in Six Dimensions and its Rotation Curve up to the edge of the halo},
  publisher = {Perimeter Institute},
  year = {2026},
  month = {may},
  note = {PIRSA:26050064 see, \url{https://pirsa.org}}
}

Abstract

The interpretation of dark matter detection experiments crucially depends on our understanding of the phase space of dark matter in the Milky Way (MW) locally, and up to the edge of the dark matter halo. A precise construction of the `entire' MW rotation curve (RC) is paramount in estimating/modelling this dark matter phase space. Recent data from the GAIA satellite has revolutionised our knowledge of the tracers with which we map the Milky Way. Yet, till date, accurate RC using GAIA is restricted only to the disk region (~ 25 kpc) while the MW halo extends an order of magnitude further. This is mainly due to the ~10 kpc GAIA parallax barrier.
 
In this talk, I will present a new GAIA-derived catalogue that breaks this barrier, and has the full 6D phase -space information of roughly 33 million tracers up to the outer halo. This is achieved by cross-matching GAIA astrometry with spectrophotometric distances and line-of-sight
velocities from 14 large-scale surveys (including DESI, SDSS-BOSS, APOGEE, LAMOST, etc), and has the best achievable yet distance-velocity estimates of roughly half a million halo stars. This multi-survey synthesis yields precise parameters and kinematics for confirmed members of distant globular clusters, dwarf galaxies, and stellar streams. This unique dataset is a gold mine for accurate multi-component mass modelling, cluster kinematics, chemical abundance mapping, galactic archaeology, dark matter searches, etc., over almost the entire Milky Way volume. As an example, I will show the very first, contiguous, most precise yet, Milky Way Rotation curve up to 250 kpc.

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