Discovery of Nuclear X-ray Sources in SINGS Galaxies
  We present the results of a search for nuclear X-ray activity in nearby
galaxies using Chandra archival data in a sample of 62 galaxies from the
Spitzer Infrared Nearby Galaxy Survey (SINGS). We detect 37 nuclear X-ray
sources; seven of these are new detections. Most of the nuclear X-ray sources
are likely to be AGNs. The fraction of galaxies hosting AGNs is thus about 60%,
much higher than that found with optical searches, and demonstrates the
efficacy of X-ray observations to find hidden AGNs in optically normal
galaxies. We find that the nuclear X-ray sources are preferentially present in
earlier type galaxies. Unlike what is observed at high redshift, we do not find
a strong correlation between the AGN luminosity and the 24 micron luminosity of
the host galaxy; we find a strong correlation with the 3.6 micron luminosity
instead. This suggests that at the present epoch the accretion rate depends on
the total mass of the galaxy, as perhaps does the black hole mass.
