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=8×10erg 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 AGN X-ray spectrum, but lies at 3×10−7 below the Eddington limit. The SED of the IC 1459 nucleus is extremely radio loud compared to normal radio-loud quasars. The nucleus is surrounded by hot ISM (kT∼0.50.6 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 ∼6×1044erg s−1, nearly four 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-100μm 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. Subject headings: Galaxies: individual (IC 1459), galaxies: nuclei, accretion, accretion disks