Computer Science
Scientific paper
Apr 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007iaus..238...93t&link_type=abstract
Black Holes from Stars to Galaxies -- Across the Range of Masses. Edited by V. Karas and G. Matt. Proceedings of IAU Symposium #
Computer Science
1
Scientific paper
According to the unified scheme of AGN, the central engine, a supermassive black hole surrounded by an accretion disc, is embedded in a toroidal dusty structure. Orientation effects lead to the Seyfert 1 / Seyfert 2 dichotomy. Single dish telescopes fail to provide the necessary resolution to resolve the circumnuclear dusty torus, the key component in this picture. We have observed four nearby AGN with the mid infrared interferometric instrument MIDI located at the VLTI to investigate the mid infrared emission with the goal to resolve the dust emission. With our measurements we resolve the dusty structure around the nucleus of the Circinus galaxy, a nearby prototype Seyfert 2 galaxy. We find an elongated structure of 0.5 × 0.7 parsec at 9 µm and 0.7 × 1.0 parsec at 12 µm. We interpret the emission to be originating in a geometrically thick dusty torus heated by the nucleus. We find this torus to be oriented perpendicular to the ionisation cone and outflow in this galaxy. It has the same size and position angle as a rotating maser disc surrounding the nucleus. Our finding hence confirms the unified picture nicely. We have also observed the nucleus of the well known radio galaxy Centaurus A and find that 70% of the mid infrared flux originates from an unresolved source with a size of less than 0.2 parsec. In this case the majority of the emission does not originate from dust but comes from a synchrotron source at the base of the radio jet. Two further galaxies, Mrk 1239 (Seyfert 1) and MCG -05-16-023 (Seyfert 2) also show unresolved mid infrared sources limiting the size of the dust distribution to less than 5 and 2 parsec respectively.
Cotton William D.
Jaffe Walter
Meisenheimer Klaus
Tristram Konrad R. W.
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