Chandra Survey of Nearby Galaxies: The Catalog

• Published in: The Astrophysical journal Vol. 835; no. 2; pp. 223 - 234
• Main Authors: She, Rui, Ho, Luis C., Feng, Hua
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01.02.2017; IOP Publishing
• Subjects: ABSORPTION; Active galactic nuclei; Astrophysics; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CHARGE-COUPLED DEVICES; CORRELATIONS; DETECTION; Elliptical galaxies; Galaxies; galaxies: active; galaxies: nuclei; GALAXY NUCLEI; Image detection; Interstellar; LUMINOSITY; PHOTONS; Polls & surveys; Power law; RESPIRATORS; Space telescopes; SPATIAL DISTRIBUTION; SPECTRA; SPECTROMETERS; Spirals; Star & galaxy formation; Star formation; STARS; Stars & galaxies; X RADIATION; X ray binaries; X ray stars; X ray telescopes; X-RAY GALAXIES; X-rays: galaxies
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/835/2/223

We searched the public archive of the Chandra X-ray Observatory as of 2016 March and assembled a sample of 719 galaxies within 50 Mpc with available Advanced CCD Imaging Spectrometer observations. 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 1037 erg s−1 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.