  Active Galactic Nuclei (AGN) play an important role in many aspects of the
modern cosmology, and of particular interest is the issue of the interplay
between AGN and their host galaxy. Using X-ray and optical data sets, we have
explored the properties of a large sample of AGNs in the Subaru/XMM-Newton Deep
Survey (SXDS) field, and studied their evolution in relation with the evolution
of their host galaxy. We present here an anticorrelation between
X-ray-to-optical flux ratio (X/O) and galaxy light concentration (C), which has
been found for the first time and might suggest that early type galaxies,
having poor matter supply to feed the AGN activity, have lower Eddington rates
than those of late type galaxies.
