The X-Ray-faint Emission of the Supermassive Nuclear Black Hole of IC 1459

Chandra observations of the supermassive black hole in the nucleus of IC 1459 show a weak (LX = 8 × 1040 ergs s-1, 0.3-8 keV), unabsorbed nuclear X-ray source, with a slope Γ = 1.88 ± 0.09, and no strong Fe K line at 6.4 keV (EW < 382 eV). This describes a normal active galactic nucleus (AGN) X-ray spectrum but lies at 3 × 10-7 below the Eddington limit. The spectral energy distribution of the IC 1459 nucleus is extremely radio-loud compared to normal radio-loud quasars. The nucleus is surrounded by a hot interstellar medium (kT ~ 0.5-0.6 keV) with an average density of 0.3 cm-3, within the central ~180 pc radius, which is comparable to the gravitational capture radius, rA ~ 140 pc. We estimate that for a standard AGN efficiency of 10%, the Bondi accretion would correspond to a luminosity of ~6 × 1044 ergs s-1, nearly 4 orders of magnitude higher than LX. ADAF solutions can explain the X-ray spectrum, but not the high radio/X-ray ratio. A jet model fits the radio-100 μm and X-ray spectra well. The total power in this jet is ~10% of LBondi, implying that accretion close to the Bondi rate is needed.