Chandra Survey of Nearby Galaxies: The Catalog
  We searched in the public archive of the Chandra X-ray Observatory as of
March 2016 and assembled a sample of 719 galaxies within 50 Mpc with ACIS
observations available. By cross-correlation with the optical or near-infrared
nuclei of these galaxies, 314 of them are identified to have an X-ray active
galactic nucleus (AGN). The majority of them are low-luminosity AGNs and are
unlikely X-ray binaries based upon their spatial distribution and luminosity
functions. The AGN fraction is around 60% for elliptical galaxies and
early-type spirals, but drops to roughly 20% for Sc and later types, consistent
with previous findings in the optical. However, the X-ray survey is more
powerful in finding weak AGNs, especially from regions with active star
formation that may mask the optical AGN signature. For example, 31% of the H II
nuclei are found to harbor an X-ray AGN. For most objects, a single power-law
model subject to interstellar absorption is adequate to fit the spectrum, and
the typical photon index is found to be around 1.8. For galaxies with a
non-detection, their stacked Chandra image shows an X-ray excess with a
luminosity of a few times 10^37 erg/s on average around the nuclear region,
possibly composed of faint X-ray binaries. This paper reports on the technique
and results of the survey; in-depth analysis and discussion of the results will
be reported in forthcoming papers.
