Name: Rachel Mason

Institution: Gemini Observatory

e-mail: rmason(no-spam)gemini.edu

Partner Contry: GS

Science Meeting: Yes

User Meeting: Yes

NGO Staff Meeting: Yes

Presentation: Yes

Format: Oral

Title: New light on old favourites: NGC1068 and NGC1097 at high spatial resolution in the mid-infrared

Co-author: C. Packham, N. Levenson, T. Geballe, M. Elitzur, J. Radomski, A. Petric, G. Wright, E. Perlman

Co-authors' Institutions: University of Florida, University of Kentucky, Gemini Observatory, Columbia University, UK Astronomy Technology Centre, Florida Institute of Technology

Abstract:

Remarkably little is known about the properties of active galactic nuclei (AGN) at the subarcsecond spatial resolution now afforded by mid-IR instrumentation on the largest ground-based telescopes. Taking advantage of Gemini's mid-IR capabilities, we are using imaging and spectroscopy with Michelle and T-ReCS to investigate the nature, extent, geometry and origin of the obscuring material thought to be responsible for the differences between AGN of types 1 and 2. Our spatially-resolved mid-IR spectra of NGC1068 show that the torus is bright, compact and embedded in diffuse emission extending over several arcseconds (~few hundred pc), with spectral properties changing significantly on <1" scales. The unresolved central source has sufficient contrast with its surroundings that we are able to fit clumpy torus models to the nuclear spectrum to constrain torus properties, but traditional larger-aperture SEDs would be significantly contaminated by emission from the narrow-line region. Low-luminosity AGN can be used to test models of the origin and dynamics of the torus, such as the torus-as-disk-wind model which predicts that below a certain luminosity the AGN cannot sustain the outflow necessary to obscure the nucleus. Our modelling of T-ReCS images of a nearby LINER shows that although thermal emission from dust is present in the central 0.5" of this AGN, the dust must be heated by the massive, compact nuclear star cluster and need not be directly associated with the AGN. These results highlight the need for detailed ground-based studies to set in context sensitive space-based observations of active galaxies at greater distances.