The relation between GC systems and SMBH in spiral galaxies: The link to the M_\bullet - M_\ast$ correlation

We explore the relationship between globular cluster total number, $N_{\rm GC}$, and central black hole mass, $M_\bullet$, in spiral galaxies. Including cosmic scatter, log $M_\bullet \propto$ (1.64 $\pm$ 0.24) log $N_{\rm GC}$. Whereas in ellipticals the correlation is linear [log $M_\bullet \propto$ (1.02 $\pm$ 0.10) log $N_{\rm GC}$], and hence could be due to statistical convergence through mergers, this mechanism cannot explain the much steeper correlation in spirals. Additionally, we derive total stellar galaxy mass, $M_\ast$, from its two-slope correlation with $N_{\rm GC}$ (Hudson et al.\ 2014) for both spirals and ellipticals. In the $M_\bullet$ versus $M_\ast$ parameter space, with $M_\ast$ derived from $N_{\rm GC}$, $M_\bullet \propto$ (1.48 $\pm$ 0.18) log $M_\ast$ for ellipticals, and $M_\bullet \propto$ (1.21 $\pm$ 0.16) log $M_\ast$ for spirals. The observed agreement between ellipticals and spirals may imply that black holes and galaxies co-evolve through ``calm” accretion, AGN feedback and other secular processes.