The images above show just 8 of 51 different nearby, late-type galaxies found to host X-ray cores near their centers. The main images are optical views and the insets show Chandra X-ray images of the same galaxies. The cross marks identify the near-infrared/optical nucleus of each galaxy, and the green ellipses show the source regions for the X-rays. A recent publication led by Rui She (Tsinghua University, China) presents a search for low-mass (<106 solar masses) black holes lurking in the centers of nearby late-type, low-mass galaxies. Many of the 51 X-ray cores discovered represent such hidden black holes. The authors use the statistics of this sample to estimate that at least 21% of late-type galaxies like those studied here host low-mass black holes at their centers. You can view the full set of X-ray core hosts below; for more information, check out the paper linked at the bottom of the page.
All 51 X-ray cores (displayed in 3 sets); see the article below for the originals.
Rui She et al 2017 ApJ 842 131. doi:10.3847/1538-4357/aa7634