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On the Disappearance of a Cold Molecular Torus around the Low-luminosity Active Galactic Nucleus of NGC 1097

T. Izumi ; K. Kohno ; K. Fathi ; E. Hatziminaoglou ; R. I. Davies ; S. Martin ; S. Matsushita ; E. Schinnerer ; D. Espada ; Susanne Aalto (Institutionen för rymd- och geovetenskap, Onsala rymdobservatorium) ; K. Onishi ; J. L. Turner ; M. Imanishi ; K. Nakanishi ; D. S. Meier ; K. Wada ; N. Kawakatu ; T. Nakajima
Astrophysical Journal Letters (2041-8205). Vol. 845 (2017), 1, p. L5.
[Artikel, refereegranskad vetenskaplig]

We used the Atacama Large Millimeter/Submillimeter Array to map the CO(3-2) and the underlying continuum emissions around the type-1low-luminosity active galactic nucleus (LLAGN; bolometric luminosity less than or similar to 10(42) erg. s(-1)) of NGC 1097 at similar to 10 pc resolution. These observations revealed a detailed cold gas distribution within a similar to 100 pc of this LLAGN. In contrast to the luminous Seyfert galaxy NGC 1068, where a similar to 7 pc cold molecular torus was recently revealed, a distinctively dense and compact torus is missing in our CO(3-2) integrated intensity map of NGC 1097. Based on the CO(3-2) flux, the gas mass of the torus of NGC 1097 would be a factor of greater than or similar to 2-3 less than that found for NGC 1068 by using the same CO-to-H-2 conversion factor, which implies less active nuclear star formation and/or inflows in NGC 1097. Our dynamical modeling of the CO(3-2) velocity field implies that the cold molecular gas is concentrated in a thin layer as compared to the hot gas traced by the 2.12 mu m H-2 emission in and around the torus. Furthermore, we suggest that NGC 1097 hosts a geometrically thinner torus than NGC 1068. Although the physical origin of the torus thickness remains unclear, our observations support a theoretical prediction that geometrically thick tori with high opacity will become deficient as AGNs evolve from luminous Seyferts to LLAGNs.

Nyckelord: galaxies: active; galaxies: individual (NGC 1097); galaxies: ISM; galaxies: Seyfert

Denna post skapades 2017-08-30.
CPL Pubid: 251523


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Institutioner (Chalmers)

Institutionen för rymd- och geovetenskap, Onsala rymdobservatorium (2010-2017)


Astronomi, astrofysik och kosmologi

Chalmers infrastruktur

Onsala rymdobservatorium