paper

High-Spatial Resolution SED of NGC 1068 from Near-IR to Radio. Disentangling the thermal and non-thermal contributions

arXiv:0804.0236 · doi:10.1051/0004-6361:200809606

Abstract

We investigate the ideas that a sizable fraction of the interferometrically unresolved infrared emission of the nucleus of NGC 1068 might originate from other processes than thermal dust emission from the torus. We examine the contribution of free-free or synchrotron emissions to the central mid- and near-IR parsec-scale emitting region of NGC 1068. Each mechanism is constrained with parsec scale radio data available for NGC 1068 in the 10^9 - 10^11 Hz regime, and compared to the highest-resolution interferometric data available in the mid-infrared. It is shown that the unresolved emission in the interferometric observation (<~1pc) is still dominatedd by dust emission and not by contributions from synchrotron or free-free emission. As recent studies suggest, the interferometric observations prefer a clumpy structure of the dust distribution. Extrapolation of the radio free-free or synchrotron emission to the IR indicates that their contribution is <20% even for the unresolved fraction of the interferometric flux. The slope of the available radio data is consistent with a power law exponent alpha = 0.29 +/- 0.07 which we interprete in terms of either free-free emission or synchrotron radiation from quasi-monochromatic electrons. We apply emission models for both mechanisms in order to obtain physical parameters. (abridged)

8 pages, 3 figures; accepted by A&A

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