Spectroscopic Confirmation of a Large Population of Active Galactic Nuclei in Clusters of Galaxies

Paul Martini, Daniel D. Kelson, Eunhyeuk Kim, John S. Mulchaey, Alex A. Athey
2006 Astrophysical Journal  
We have completed a spectroscopic survey of X-ray point sources in eight low-redshift clusters of galaxies (0.0510^41) 5 stress that additional, lower-luminosity AGN are expected to be present in the M_R < -20 mag cluster members. Our data unambiguously demonstrate that cluster galaxies host AGN more frequently than previously expected. Only four of these galaxies have obvious visible-wavelength AGN signatures, even though their X-ray luminosities are too high for their X-ray emission to be due
more » ... to populations of low-mass X-ray binaries or hot, gaseous halos. We attribute the significant difference in visible and X-ray AGN identification to dilution of low-luminosity AGN spectral signatures by host galaxy starlight and/or obscuration of accretion onto the central, supermassive black hole.
doi:10.1086/503521 fatcat:y4wz56nacvc65g4lnp5xnanrua