AChandraX‐Ray Study of Cygnus A. II. The Nucleus

We report Chandra ACIS and quasi-simultaneous RXTE observations of thenearby, powerful radio galaxy Cygnus A, with the present paper focusing on theproperties of the active nucleus. In the Chandra observation, the hard (> a fewkeV) X-ray emission is spatially unresolved with a size \approxlt 1 arcsec (1.5kpc, H_0 = 50 km s^-1 Mpc^-1) and coincides with the radio and near infrarednuclei. In contrast, the soft (< 2 keV) emission exhibits a bi-polar nebulositythat aligns with the optical bi-polar continuum and emission-line structuresand approximately with the radio jet. In particular, the soft X-ray emissioncorresponds very well with the [O III] \lambda 5007 and H\alpha + [N II]\lambda\lambda 6548, 6583 nebulosity imaged with HST. At the location of thenucleus there is only weak soft X-ray emission, an effect that may be intrinsicor result from a dust lane that crosses the nucleus perpendicular to the sourceaxis. The spectra of the various X-ray components have been obtained bysimultaneous fits to the 6 detectors. The compact nucleus is detected to 100keV and is well described by a heavily absorbed power law spectrum with\Gamma_h = 1.52^{+0.12}_{-0.12} (similar to other narrow line radio galaxies)and equivalent hydrogen column N_H (nuc) = 2.0^{+0.1}_{-0.2} \times 10^{23}cm^-2. (Abstract truncated).Comment: To be published in the Astrophysical Journal, v564 January 1, 2002 issue; 34 pages, 11 figures (1 color