2003ApJ...588..763D

We analyze recent simultaneous Chandra/RXTE observations of the Seyfert 2 galaxy NGC 4945. The unprecedented spatial resolution of Chandra means we are able to separate the spectra of the nucleus, starburst, and superwind regions, while the RXTE data extend the spectrum to higher energies. The extreme absorbing column of N_H∼4x10²⁴ cm^–2 means that the nucleus is only directly seen above 8-10 keV, while the lower energy spectrum from the nuclear region in Chandra is dominated by reflection. By contrast, the superwind is dominated by emission from hot plasma, but the starburst region contains both hot plasma and reflection signatures. Forming a reflected spectrum requires that the starburst region contain clumps of cool, optically thick material, perhaps star-forming cores, which are irradiated by 7-10 keV photons from the nucleus. Since photons of this energy are obscured along the line of sight, this confirms the result of Madejski et al. that the extreme absorption material is disklike rather than toroidal. However, the IR/optical limits on the lack of high-excitation emission lines show that, by contrast, the lower energy photons from the nucleus are obscured in all directions. We discuss the complex absorption structure revealed by these observations and propose an overall source geometry in which the nucleus is completely embedded in material with N_H∼10²³ cm^–2.