Space Science Reviews

, Volume 100, Issue 1–4, pp 129–138

Mass distribution in our Galaxy

  • Ortwin Gerhard


This article summarizes recent work on the luminosity and mass distribution of the galactic bulge and disk, and on the mass of the Milky Way's dark halo. A new luminosity model consistent with the COBE NIR data and the apparent magnitude distributions of bulge clump giant stars has bulge/bar length of ≃3.5 kpc, axis ratios of 1:(0.3–0.4):0.3, and short disk scale-length (≃2.1 kpc). Gas-dynamical flows in the potential of this model with constant M/L fit the terminal velocities in 10° le|l|le50° very well. The luminous mass distribution with this M/L is consistent with the surface density of known matter near the Sun, but still underpredicts the microlensing optical depth towards the bulge. Together, these facts argue strongly for a massive, near-maximal disk in our ∼L*, Sbc spiral galaxy. While the outer rotation curve and global mass distribution are not as readily measured as in similar spiral galaxies, the dark halo mass estimated from satellite velocities is consistent with a flat rotation curve continuing on from the luminous mass distribution.


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Copyright information

© Kluwer Academic Publishers 2002

Authors and Affiliations

  • Ortwin Gerhard
    • 1
  1. 1.Astronomisches InstitutUniversität BaselSwitzerland

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