The Ubiquity of Supermassive Black Holes in the Hubble Sequence
  We present the results of a study of a statistically significant sample of
galaxies which clearly demonstrate that supermassive black holes are
generically present in all morphological types. Our analysis is based on the
quantitative morphological classification of 1.12 million galaxies in the SDSS
DR7 and on the detection of black hole activity via two different methods, the
first one based on their X-ray/radio emission and the second one based on their
mid-infrared colors. The results of the first analysis confirm the correlation
between black hole and total stellar mass for 8 galaxies and includes one
galaxy classified as bulgeless. The results of our second analysis, consisting
of 15,991 galaxies, show that galaxies hosting a supermassive black hole follow
the same morphological distribution as the general population of galaxies in
the same redshift range. In particular, the fraction of bulgeless galaxies,
1,450 galaxies or 9 percent, is found to be the same as in the general
population. We also present the correlation between black hole and total
stellar mass for 6,247 of these galaxies. Importantly, whereas previous studies
were limited to primarily bulge-dominated systems, our study confirms this
relationship to all morphological types, in particular, to 530 bulgeless
galaxies. Our results indicate that the true correlation that exists for
supermassive black holes and their host galaxies is between the black hole mass
and the total stellar mass of the galaxy and hence, we conclude that the
previous assumption that the black hole mass is correlated with the bulge mass
is only approximately correct.
