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Velocity Dispersions.

- Gephardt uses the rms dispersion within a slit aperture of 2re (σ1).
- FM use the rms dispersion at re/8 (σ8)

.

  • But actually, FM only extrapolate this value from central velocity dispersions

  • From Jørgensen, Franx & Kjaergaard 1995:

  • Using a sample of 40 well-sampled galaxies, they dynamically derive the relation:

  • Central velocity dispersions may also be contaminated by the influence of the central black hole.

Jørgensen, Franx & Kjaergaard 1995