We present the first results from AMUSE-Field , a Chandra survey designed to characterize the occurrence and intensity of low-level accretion onto supermassive black holes ( SMBHs ) at the center of local early-type field galaxies .
This is accomplished by means of a Large Program targeting a distance-limited ( < 30 Mpc ) sample of 103 early types spanning a wide range in stellar masses .
We acquired new ACIS-S observations for 61 objects down to a limiting ( 0.3–10 keV ) luminosity of 2.5 \times 10 ^ { 38 } erg s ^ { -1 } , and we include an additional 42 objects with archival ( typically deeper ) coverage .
A nuclear X-ray source is detected in 52 out of the 103 galaxies .
After accounting for potential contamination from low-mass X-ray binaries , we estimate that the fraction of accreting SMBHs within the sample is 45 \pm 7 % , which sets a firm lower limit on the occupation fraction within the field .
The measured nuclear X-ray luminosities are invariably highly sub-Eddington , with L _ { X } / L _ { Edd } ratios between \sim 10 ^ { -4 } – 10 ^ { -8 } .
As also found in a companion survey targeting Virgo early types , the active fraction increases with increasing host galaxy stellar mass , reflective of “ Eddington incompleteness ” within the lower-mass objects .
For the Field sample , the average nuclear X-ray luminosity scales with the host stellar mass as M _ { star } ^ { 0.71 \pm 0.10 } , with an intrinsic scatter of 0.73 \pm 0.09 dex .
Qualitatively similar results hold for morphologically homogeneous ( type E ) or uniform sensitivity ( new observations only ) subsets .
A majority of the AMUSE-Field galaxies ( 78 % ) inhabits groups , enabling us to investigate the influence of group richness upon nuclear activity .
We see no evidence for a positive correlation between nuclear X-ray luminosity , normalized to host properties , and galaxy density .
Rather , while the scatter is substantial , it appears that the Eddington-scaled X-ray luminosity of group members may be slightly lower than for isolated galaxies , and that this trend continues to cluster early-types .