The Complex Circumnuclear Environment of the Broad-line Radio Galaxy 3C 390.3 Revealed by Chandra HETG

Abstract

We present the first high spectral resolution X-ray observation of the broad-line radio galaxy 3C 390.3 obtained with the high-energy transmission grating spectrometer on board the Chandra X-ray Observatory. The spectrum shows complex emission and absorption features in both the soft X-rays and Fe K band. We detect emission and absorption lines in the energy range E = 700-1000 eV associated with ionized Fe L transitions (Fe XVII-XX). An emission line at the energy of E ≃ 6.4 keV consistent with the Fe Kα is also observed. Our best-fit model requires at least three different components: (I) a hot emission component likely associated with the hot interstellar medium in this elliptical galaxy with temperature kT = 0.5 ± 0.1 keV; (II) a warm absorber with ionization parameter logξ = 2.3 ± 0.5 erg s<SUP>-1</SUP> cm, column density logN <SUB>H</SUB> = 20.7 ± 0.1 cm<SUP>-2</SUP>, and outflow velocity v <SUB>out</SUB> < 150 km s<SUP>-1</SUP> and (III) a lowly ionized reflection component in the Fe K band likely associated with the optical broad-line region or the outer accretion disk. These evidences suggest the possibility that we are looking directly down the ionization cone of this active galaxy and that the central X-ray source only photoionizes along the unobscured cone. This is overall consistent with the angle-dependent unified picture of active galactic nuclei.