Supermassive black holes in disk-dominated galaxies outgrow their bulges
  and co-evolve with their host galaxies
  The deep connection between galaxies and their supermassive black holes is
central to modern astrophysics and cosmology. The observed correlation between
galaxy and black hole mass is usually attributed to the contribution of major
mergers to both. We make use of a sample of galaxies whose disk-dominated
morphologies indicate a major-merger-free history and show that such systems
are capable of growing supermassive black holes at rates similar to quasars.
Comparing black hole masses to conservative upper limits on bulge masses, we
show that the black holes in the sample are typically larger than expected if
processes creating bulges are also the primary driver of black hole growth. The
same relation between black hole and total stellar mass of the galaxy is found
for the merger-free sample as for a sample which has experienced substantial
mergers, indicating that major mergers do not play a significant role in
controlling the coevolution of galaxies and black holes. We suggest that more
fundamental processes which contribute to galaxy assembly are also responsible
for black hole growth.
