X-Ray Properties of Intermediate-Mass Black Holes in Active Galaxies
Abstract
We present a pilot study of the X-ray properties of intermediate-mass (~105-106 Msolar) 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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- February 2007
- DOI:
- 10.1086/509064
- arXiv:
- arXiv:astro-ph/0608061
- Bibcode:
- 2007ApJ...656...84G
- Keywords:
-
- Galaxies: Active;
- Galaxies: Nuclei;
- Galaxies: Seyfert;
- X-Rays: Galaxies;
- Astrophysics
- E-Print:
- Submitted to ApJ on 7 April 2006, but still awaiting referee's report