Galaxies and supermassive black holes in the local universe: the Velocity Dispersion Function and Black Hole Mass Function
Abstract
We study the distribution of velocity dispersions, σ, and supermassive black hole masses, MBH, for galaxies in the SDSS at 0.03 ≤ z ≤ 0.1. We construct the velocity dispersion function (VDF) and the Black Hole Mass Function (BHMF) from a sample complete for all σ, where galaxies with σ greater than the σ-completeness limit of the SDSS spectroscopic survey are included. We compare two different σ estimates; one based on SDSS spectroscopy (σspec) and another on photometric estimates (σmod) and find that the VDF measured from σspec rises gently with decreasing σ, while the VDF from σmod falls with σ. The shape of our σspec VDF is in close agreement with previous determinations for the local universe; however, the σmod VDF doesn't reproduce the typically observed results from spectroscopy, implying that rotational velocity may affect σspec measurements. In fact, both late and early type galaxies have σspec > σmod, suggesting that the rotational component of most galaxies figure significantly into σspec measurements. Early-type galaxies dominate the population of high σ galaxies, while late-type galaxies dominate the low σ statistic. Very few galaxies are observed to have σ > 350 km s-1. The BHMF derived from the VDF requires many more SMBHs with masses 6 ≤ log(MBH/M⊙) ≤ 8 than larger ones with log(MBH/M⊙) > 9. Assuming an average radiative efficiency, the mass density accreted by local SMBHs matches that observed from high-redshift AGNs, implying that the same phenomenon powers both types of objects and that mass accretion is the primary mode of growing SMBHs.
- Publication:
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American Astronomical Society Meeting Abstracts #233
- Pub Date:
- January 2019
- Bibcode:
- 2019AAS...23314522H