Supermassive Black Holes (SMBHs) have been found to reside in the centers of the majority of the massive galaxies in the nearby Universe. The tight correlations that the mass of the SMBHs follows with the properties of the host galaxy, such as the stellar mass, the velocity dispersion or the luminosity, suggest a coordinated formation and evolution by a common physical mechanism. However, some galaxies have been found to strongly deviate from these relations, challenging this assumed co-evolution. 

 

In particular, it has been pointed out that most candidates to relic galaxies  (see Local Massive Compact galaxies section for more information on why they are special) seem to host extremely large SMBHs, nick-named übermassive SMBHs. In my latest work, I have investigated a scenario that could explain the nature of such deviations for such types of galaxies. I have found that all relic galaxies should deviate from the relations between SMBHs and the galaxy, thus having larger SMBHs than expected, due to the uncommon evolutionary path they follow. It is assumed that massive galaxies undergo a two-phase of formation: first, the central massive core is formed fast and furious at high redshift, and then the galaxy changes its morphology and increases in size due to the accretion in its outskirts of new material from merging satellites. However, our relic galaxies skip this second phase, staying compact and massive over cosmic time. But by then, their SMBH is fully in place, pointing towards a decoupling between the formation of the SMBHs and the massive galaxy (see the schematic cartoon below).