The black hole mass function derived from local spiral galaxies

We present our determination of the nuclear supermassive black hole (SMBH) mass function for spiral galaxies in the local universe, established from a volume-limited sample consisting of a statistically complete collection of the brightest spiral galaxies in the southern (δ < 0°) hemisphere. Our SMBH mass function agrees well at the high-mass end with previous values given in the literature. At the low-mass end, inconsistencies exist in previous works that still need to be resolved, but our work is more in line with expectations based on modeling of black hole evolution. This low-mass end of the spectrum is critical to our understanding of the mass function and evolution of black holes since the epoch of maximum quasar activity. The sample is defined by a limiting luminosity (redshift-independent) distance, D L = 25.4 Mpc (z = 0.00572) and a limiting absolute B-band magnitude, . These limits define a sample of 140 spiral galaxies, with 128 measurable pitch angles to establish the pitch angle distribution for this sample. This pitch-angle distribution function may be useful in the study of the morphology of late-type galaxies. We then use an established relationship between the logarithmic spiral arm pitch angle and the mass of the central SMBH in a host galaxy in order to estimate the mass of the 128 respective SMBHs in this volume-limited sample. This result effectively gives us the distribution of mass for SMBHs residing in spiral galaxies over a lookback time, t L ≤ 82.1 Myr and contained within a comoving volume, V C = 3.37 × 10⁴ Mpc³. We estimate that the density of SMBHs residing in spiral galaxies in the local universe is × 10 ⁴ MMpc^-3. Thus, our derived cosmological SMBH mass density for spiral galaxies is × 10^-7 h 67.77. Assuming that black holes grow via baryonic accretion, we predict that % of the universal baryonic inventory (ΩBH/ωb) is confined within nuclear SMBHs at the center of spiral galaxies.