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 _ { \ast } \mathrel { \hbox { \hbox to 0.0 pt { \hbox { \lower 3.0 pt \hbox { $ \sim$ } } } \hbox { % \raise 2.0 pt \hbox { $ > $ } } } } 10 ^ { 10 } ~ { } M _ { \odot } ) 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 ( 4.2 \times 10 ^ { 6 } and 1.2 \times 10 ^ { 7 } ~ { } M _ { \odot } ) and place lower limits on black hole masses for the remaining sample ( typically M _ { \mathrm { BH } } \mathrel { \hbox { \hbox to 0.0 pt { \hbox { \lower 3.0 pt \hbox { $ \sim$ } } } % \hbox { \raise 2.0 pt \hbox { $ > $ } } } } 10 ^ { 6 } ~ { } M _ { \odot } ) , 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 } \approx 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 .