Two channels of supermassive black hole growth as seen on the galaxies mass-size plane

Understand

We investigate the variation of black hole masses (Mbh) as a function of their host galaxy stellar mass (Mstar) and half-light radius (Re).

• We confirm that the scatter in Mbh within this plane is essentially the same as that in the Mbh - sigma relation, as expected from the negligible scatter reported in the virial mass estimator sigma_v^2=GxMstar/(5xRe).
• All variation in Mbh happens along lines of constant sigma_v on the (Mstar, Re) plane, or Mstar $\propto$ Re for Mstar <2x10^11 Msun.
• This trend is qualitatively the same as those previously reported for galaxy properties related to stellar populations, like age, metallicity, alpha enhancement, mass-to-light ratio and gas content.