A Direct Image of the Inner Torus of NGC 1068 |
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Authors: | JF Gallimore SA Baum CP O'Dea |
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Institution: | (1) Max-Planck-Institut für extraterrestrische Physik, Postfach 1603, Giessenbachstrasse, D-85740 Garching b. München, Germany;(2) Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD, 21218 |
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Abstract: | We present the first VLBI observations of the compact source S1 in the radio jet of NGC 1068. Roughly 1 pc in length and 0.2
pc wide, S1 resolves into clumps aligned perpendicular to the local radio jet axis. The radio continuum emission arises from
a hot (Te ~ 106 K), dense (ne ~ 106 cm-3) plasma, and the source of the radio emission is either thermal free-free emission
or Thomson-reflected synchrotron emission. The clouds comprising S1 are opaque to soft X-radiation, and we therefore propose
that S1 is the inner, ionized region, or ‘hot zone,’ of the obscuring medium surrounding the active nucleus. The covering
fraction of the hot zone is small, Cf ⋦ 10%. Since the covering fraction of the dusty, obscuring medium is probably much larger,
the obscuring disk must either flare or warp outside of the hot zone. That the radio jet and hot zone axes are perpendicular
also suggests that the hot zone may be considered to trace the outermost extent of the accretion disk.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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