We aim to explore the relationship between globular cluster total number , N _ { GC } , and central black hole mass , M _ { \bullet } , in spiral galaxies , and compare it with that recently reported for ellipticals .
We present results for the Sbc galaxy NGC 4258 , from Canada France Hawaii Telescope data .
Thanks to water masers with Keplerian rotation in a circumnuclear disk , NGC 4258 has the most precisely measured extragalactic distance and supermassive black hole mass to date .
The globular cluster ( GC ) candidate selection is based on the ( u ^ { * } - i ^ { \prime } ) vs. ( i ^ { \prime } - K _ { s } ) diagram , which is a superb tool to distinguish GCs from foreground stars , background galaxies , and young stellar clusters , and hence can provide the best number counts of GCs from photometry alone , virtually free of contamination , even if the galaxy is not completely edge-on .
The mean optical and optical-near infrared colors of the clusters are consistent with those of the Milky Way and M 31 , after extinction is taken into account .
We directly identify 39 GC candidates ; after completeness correction , GC luminosity function extrapolation and correction for spatial coverage , we calculate a total N _ { GC } = 144 \pm 31 ^ { +38 } _ { -36 } ( random and systematic uncertainties , respectively ) .
We have thus increased to 6 the sample of spiral galaxies with measurements of both M _ { \bullet } and N _ { GC } .
NGC 4258 has a specific frequency S _ { N } = 0.4 \pm 0.1 ( random uncertainty ) , and is consistent within 2 \sigma with the N _ { GC } vs . M _ { \bullet } correlation followed by elliptical galaxies .
The Milky Way continues to be the only spiral that deviates significantly from the relation .