We have examined the relationship between supermassive black hole mass ( M _ { \mathrm { BH } } ) and the stellar mass of the host spheroid ( M _ { \mathrm { sph,* } } ) for a sample of 75 nearby galaxies .
To derive the spheroid stellar masses we used improved 2MASS K _ { \mathrm { \it s } } -band photometry from the archangel photometry pipeline .
Dividing our sample into core-Sérsic and Sérsic galaxies , we find that they are described by very different M _ { \mathrm { BH } } –M _ { \mathrm { sph,* } } relations .
For core-Sérsic galaxies — which are typically massive and luminous , with M _ { BH } \gtrsim 2 \times 10 ^ { 8 } { M } _ { \odot } — we find M _ { \mathrm { BH } } \propto M _ { \mathrm { sph,* } } ^ { 0.97 \pm 0.14 } , consistent with other literature relations .
However , for the Sérsic galaxies — with typically lower masses , M _ { \mathrm { sph,* } } \lesssim 3 \times 10 ^ { 10 } M _ { \odot } — we find M _ { \mathrm { BH } } \proptoM _ { \mathrm { sph,* } } ^ { 2.22 \pm 0.58 } , a dramatically steeper slope that differs by more than 2 standard deviations .
This relation confirms that , for Sérsic galaxies , M _ { \mathrm { BH } } is not a constant fraction of M _ { \mathrm { sph,* } } .
Sérsic galaxies can grow via the accretion of gas which fuels both star formation and the central black hole , as well as through merging .
Their black hole grows significantly more rapidly than their host spheroid , prior to growth by dry merging events that produce core-Sérsic galaxies , where the black hole and spheroid grow in lock step .
We have additionally compared our Sérsic M _ { \mathrm { BH } } –M _ { \mathrm { sph,* } } relation with the corresponding relation for nuclear star clusters , confirming that the two classes of central massive object follow significantly different scaling relations .