Dark and luminous mass components of Omega Centauri from stellar kinematics

Journal Article · 30 January 2022 · Monthly Notices of the Royal Astronomical Society

DOI: https://doi.org/10.1093/mnras/stac261 · OSTI ID:1979556

Evans, Addy J.  ^[1]; Strigari, Louis E.  ^[2]; Zivick, Paul ^[2]

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1. Texas A & M University, College Station, TX (United States); Texas A & M Univ., College Station, TX (United States)
2. Texas A & M University, College Station, TX (United States)

Here we combine proper motion data from Gaia EDR₃ and HST with line-of-sight velocity data to study the stellar kinematics of the ω Cen globular cluster. Using a steady-state, axisymmetric dynamical model, we measure the distribution of both the dark and luminous mass components. Assuming both Gaussian and Navarro–Frenk–White mass profiles, depending on the data set, we measure an integrated mass of ≲10⁶ M_⊙ within the ω Cen half-light radius for a dark component that is distinct from the luminous stellar component. For the HST and radial velocity data, models with a non-luminous mass component are strongly statistically preferred relative to a stellar mass-only model with a constant mass-to-light ratio. While a compact core of stellar remnants may account for a dynamical mass up to ~5 x 10⁵ M_⊙, they likely cannot explain the higher end of the range. This leaves open the possibility that this non-luminous dynamical mass component comprises non-baryonic dark matter. In comparison to the dark matter distributions around dwarf spheroidal galaxies, the ω Cen dark mass component is much more centrally concentrated. Interpreting the non-luminous mass distribution as particle dark matter, we use these results to obtain the J-factor, which sets the sensitivity to the annihilation cross-section. For the data sets considered, the range of median J-factors is ~10²²-10²⁴ GeV² cm^-5, which is larger than that obtained for any dwarf spheroidal galaxy.

• Research Organization: Texas A & M University, College Station, TX (United States)
• Sponsoring Organization: Texas A&M University; USDOE Office of Science (SC)
• Grant/Contract Number: SC0010813
• OSTI ID: 1979556
• Journal Information: Monthly Notices of the Royal Astronomical Society, Journal Name: Monthly Notices of the Royal Astronomical Society Journal Issue: 3 Vol. 511; ISSN 0035-8711
• Publisher: Oxford University PressCopyright Statement
• Country of Publication: United States
• Language: English