2006/08/02 by Jenny E. Greene, Luis C. Ho · 1 citation
Physics and Astronomy · #Active galactic nucleus #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Cosmic Phenomena #Black hole (networking) #Eddington luminosity #Flux (metallurgy) #Galaxies: Formation, Evolution, Phenomena #Galaxy #Luminosity #Optics #Physics #X-ray #astro-ph
paper · pdf · doi:10.1086/509064
published as Astrophys.J.656:84-92,2007 · Submitted to ApJ on 7 April 2006, but still awaiting referee's report; 8 pages, 4 figures, uses emulateapj5.sty
arxiv created 2006/08/02 · openalex publication_date 2007/02/03 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We present a pilot study of the X-ray properties of intermediate-mass (~10 5 -10 6 M ☉ ) black holes in active galaxies using the Chandra X-ray telescope. Eight of the 10 active galaxies are detected with a significance of at least 3 σ, with X-ray luminosities in the range L 0.5-2 keV ≈ 10 41 -10 43 ergs s -1 . The optical to X-ray flux ratios are consistent with expectations, given the known correlations between α ox and ultraviolet luminosity, while a couple of objects appear to be anomalously X-ray weak. The range of 0.5 to 2 keV photon indices we measure, 1 < Γ s < 2.7, is entirely consistent with values found in samples of more luminous sources with more massive black holes. Black hole mass is evidently not a primary driver of soft X-ray spectral index. On the other hand, we do find evidence for a correlation between the X-ray power-law slope and both X-ray luminosity and Eddington ratio, which may suggest that X-ray emission mechanisms weaken at high Eddington ratios. Such a weakening may explain the anomalous X-ray weakness of one of our most optically luminous objects.