X-RAY EVIDENCE FOR SEYFERT ACTIVITY BURIED IN THE INFRARED GALAXY NGC-4945

We have observed the infrared galaxy NGC 4945 using the Japanese X-ray astronomy satellite, Ginga. The X-ray spectrum is found to be composed of three components: hard X-ray emission which is heavily absorbed by cold material with column density of about 10(24.7) cm-2; a soft X-ray component seen in the 2-10 keV band; and an iron emission line, The hard component exhibits a power-law spectrum with photon index of about 1.7. The mean X-ray luminosity in the 2-20 keV band, after correction for absorption is 3 x 10(42) ergs s-1 with significant intensity variation on a time scale of several hours. These results are thought to be evidence for an AGN (active galactic nucleus) in the galaxy. The X-ray spectrum of the soft component can be fitted with a power-law model having nearly the same photon index, but the luminosity is only 3% that of the hard component. The soft component shows no time variability. The energy of the iron line is found to be 6.5 +/- 0.1 keV, and the equivalent width is 1.5 +/- 0.3 keV. The X-ray spectrum is interpreted to be composed of the X-ray emission from a hidden Seyfert nucleus behind an obscuring torus, the scattered continuum radiation, and a fluorescence line emission from ionized iron in the scattering medium. Thus NGC 4945 is the first example of an active galaxy which exhibits both the obscuring and scattering picture of the type 2 AGN.