A. Marinucci, G. Risaliti, Junfeng Wang, E. Nardini, M. Elvis, G. Fabbiano, S. Bianchi, G. Matt
We present a time, spectral and imaging analysis of the X-ray reflector in
NGC 4945, which reveals its geometrical and physical structure with
unprecedented detail. NGC 4945 hosts one of the brightest AGN in the sky above
10 keV, but it is only visible through its reflected/scattered emission below
10 keV, due to absorption by a column density of ~4\times10^24 cm-2. A new
Suzaku campaign of 5 observations spanning ~6 months, together with past
XMM-Newton and Chandra observations, show a remarkable constancy (within <10%)
of the reflected component. Instead, Swift-BAT reveals strong intrinsic
variability on time scales longer than one year. Modeling the circumnuclear gas
as a thin cylinder with the axis on the plane of the sky, we show that the
reflector is at a distance >30-50 pc, well within the imaging capabilities of
Chandra at the distance of NGC 4945 (1"~18 pc). Accordingly, the Chandra
imaging reveals a resolved, flattened, ~150 pc-long clumpy structure, whose
spectrum is fully due to cold reflection of the primary AGN emission. The
clumpiness may explain the small covering factor derived from the spectral and
variability properties.
View original:
http://arxiv.org/abs/1202.1279
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