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THE 3-5 µ m SPECTRUM OF NGC 1068 AT HIGH ANGULAR RESOLUTION: DISTRIBUTION OF EMISSION AND ABSORPTION FEATURES ACROSS THE NUCLEAR CONTINUUM SOURCE

journal contribution
posted on 2023-06-08, 07:09 authored by T R Geballe, R E Mason, A Rodríguez-Ardila, D J Axon
We report moderate resolution 3-5 mu m spectroscopy of the nucleus of NGC 1068 obtained at 0 ''.3 (20 pc) resolution with the spectrograph slit aligned approximately along the ionization cones of the active galactic nucleus. The deconvolved full width at half-maximum of the nuclear continuum source in this direction is 0 ''.3. Four coronal lines of widely different excitations were detected; the intensity of each peaks near radio knot C, approximately 0 ''.3 north of the infrared continuum peak, where the radio jet changes direction. Together with the broadened line profiles observed near that location, this suggests that shock ionization is the dominant excitation mechanism of the coronal lines. The depth of the 3.4 mu m hydrocarbon absorption is maximum at and just south of the continuum peak, similar to the 10 mu m silicate absorption. That and the similar and rapid variations of the optical depths of both features across the nucleus suggest that substantial portions of both arise in a dusty environment just in front of the continuum source(s). A new and tighter limit is set on the column density of CO. Although clumpy models of the dust screen might explain the shallowness of the silicate feature, the presence of the 3.4 mu m feature and the absence of CO are strongly reminiscent of Galactic diffuse cloud environments and a consistent explanation for them and the observed silicate feature is found if all three phenomena occur in such an environment, existing as close as 10 pc to the central engine.

History

Publication status

  • Published

Journal

Astrophysical Journal

ISSN

0004-637X

Publisher

Institute of Physics

Issue

2

Volume

701

Page range

1710-1720

Department affiliated with

  • Physics and Astronomy Publications

Full text available

  • No

Peer reviewed?

  • Yes

Legacy Posted Date

2012-02-06

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