Galaxy Zoo: Bulgeless Galaxies With Growing Black Holes
  The growth of supermassive black holes appears to be driven by galaxy
mergers, violent merger-free processes and/or `secular' processes. In order to
quantify the effects of secular evolution on black hole growth, we study a
sample of active galactic nuclei (AGN) in galaxies with a calm formation
history free of significant mergers, a population that heretofore has been
difficult to locate. Here we present an initial sample of 13 AGN in massive
(M_* >~ 1e10 M_sun) bulgeless galaxies -- which lack the classical bulges
believed inevitably to result from mergers -- selected from the Sloan Digital
Sky Survey using visual classifications from Galaxy Zoo. Parametric
morphological fitting confirms the host galaxies lack classical bulges; any
contributions from pseudobulges are very small (typically < 5%). We compute
black hole masses for the two broad-line objects in the sample (4.2e6 and 1.2e7
M_sun) and place lower limits on black hole masses for the remaining sample
(typically M_BH >~ 1e6 M_sun), showing that significant black hole growth must
be possible in the absence of mergers or violent disk instabilities.
  The black hole masses are systematically higher than expected from
established bulge-black hole relations. However, if the mean Eddington ratio of
the systems with measured black hole masses (L/L_Edd = 0.065) is typical, 10 of
13 sources are consistent with the correlation between black hole mass and
total stellar mass. That pure disk galaxies and their central black holes may
be consistent with a relation derived from elliptical and bulge-dominated
galaxies with very different formation histories implies the details of stellar
galaxy evolution and dynamics may not be fundamental to the co-evolution of
galaxies and black holes.
