X-ray properties of intermediate-mass black holes in active galaxies

Jenny E. Greene, Luis C. Ho

Research output: Contribution to journalArticlepeer-review

61 Scopus citations


We present a pilot study of the X-ray properties of intermediate-mass (∼105-106 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 L0.5-2 kev ≈ 1041-1043 ergs s -1. The optical to X-ray flux ratios are consistent with expectations, given the known correlations between αox 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 < Γs < 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.

Original languageEnglish (US)
Pages (from-to)84-92
Number of pages9
JournalAstrophysical Journal
Issue number1 I
StatePublished - Feb 10 2007
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Galaxies: active
  • Galaxies: nuclei
  • Galaxies: seyfert
  • X-rays: galaxies


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