Galaxies and Supermassive Black Holes at z <= 0.1: The Velocity Dispersion Function

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We study the distribution of central velocity dispersion, sigma, for >100000 galaxies in the SDSS at 0.01 <= z <= 0.1.

• We construct the velocity dispersion function (VDF) from samples complete for all sigma, where galaxies with sigma greater than the sigma-completeness limit of the SDSS spectroscopic survey are included.
• We compare two different sigma estimates; one based on SDSS spectroscopy (sigma_spec) and another on photometric estimates (sigma_mod).
• The sigma_spec for our sample is systematically higher than sigma_mod for all ranges of sigma, implying that rotational velocity may affect sigma_spec measurements.