To better understand the mechanism or mechanisms that lead to AGN activity today , we measure the X-ray AGN fraction in a new sample of nearby clusters and examine how it varies with galaxy properties , projected cluster-centric radius , and cluster velocity dispersion .
We present new wide-field Chandra X-ray Observatory observations of Abell 85 , Abell 754 and the background cluster Abell 89B out to their virial radii .
Out of seventeen X-ray sources associated with galaxies in these clusters , we classify seven as X-ray AGN with L _ { X,B } > 10 ^ { 41 } { erg s } ^ { -1 } .
Only two of these would be classified as AGN based on their optical spectra .
We combine these observations with archival data to create a sample of X-ray AGN from six z < 0.08 clusters and find that 3.4 ^ { +1.1 } _ { -0.8 } \% of M _ { R } < -20 galaxies host X-ray AGN with L _ { X,B } > 10 ^ { 41 } { erg s } ^ { -1 } .
We find that more X-ray AGN are detected in more luminous galaxies and attribute this to larger spheriods in more luminous galaxies and increased sensitivity to lower Eddington-rate accretion from black holes in those spheroids .
At a given X-ray luminosity limit , more massive black holes can be accreting less efficiently , yet still be detected .
If interactions between galaxies are the principal drivers of AGN activity , then the AGN fraction should be higher in lower velocity dispersion clusters and the outskirts of clusters .
However , the tendency of the most massive and early-type galaxies to lie in the centers of the richest clusters could dilute such trends .
While we find no variation in the AGN fraction with projected cluster-centric radius , we do find that the AGN fraction increases significantly from 2.6 ^ { +1.0 } _ { -0.8 } \% in rich clusters to 10.0 ^ { +6.2 } _ { -4.3 } \% in those with lower velocity dispersions .