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Abstract

Suzaku observed a nearby Seyfert2 galaxy, NGC 4945, which hosts one of the brightest active galactic nuclei above 20keV. Combining data from the two detectors aboard Suzaku, the AGN intrinsic nuclear emission and its reprocessed signals were observed simultaneously. The intrinsic emission is highly obscured with an absorbing column of |$\sim$|5|$\times 10^{24}$|cm|$^{-2}$|⁠. The spectrum below 10keV is dominated by a reflection continuum and emission lines from neutral/ionized material. Along with a neutral iron K|$\alpha$| line, a neutral iron K|$\beta$| line and a neutral nickel K|$\alpha$| line were detected for the first time from this source. The neutral lines and the cold reflection continuum are consistent with both originating in the same location. The Compton down-scattered shoulder in the neutral Fe-K|$\alpha$| line is |$\sim 10\%$| in flux of the narrow core, which confirms that the line originates from reflection, rather than transmission. The flux of the intrinsic emission varied by a factor of |$\sim 2$| within |$\sim 20$|ks, which requires the obscuring material to be geometrically thin. Broadband spectral modeling showed that the solid angle of the neutral reflector is less than a few |$\times 10^{-2} \times 2\pi$|⁠. All of this evidence regarding the reprocessed signals suggests that a disk-like absorber/reflector is viewed from a near edge-on angle.

© 2008 Astronomical Society of Japan
Subject
galaxies: active galaxies: individual galaxies: Seyfert X-rays: galaxies
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