On the Disappearance of a Cold Molecular Torus around the Low-luminosity Active Galactic Nucleus of NGC 1097
Artikel i vetenskaplig tidskrift, 2017

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.

galaxies: individual (NGC 1097)

galaxies: Seyfert

galaxies: ISM

galaxies: active


T. Izumi

National Astronomical Observatory of Japan

K. Kohno

University of Tokyo

Research Center for the Early Universe

K. Fathi

Valhallav. 67

E. Hatziminaoglou

European Southern Observatory (ESO)

R. I. Davies


S. Martin

Atacama Large Millimeter-submillimeter Array (ALMA)

European Southern Observatory Santiago

S. Matsushita

Academia Sinica

E. Schinnerer


D. Espada

The Graduate University for Advanced Studies (SOKENDAI)

National Astronomical Observatory of Japan

Susanne Aalto

Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium

K. Onishi

Ehime University

J. L. Turner

University of California

M. Imanishi

National Astronomical Observatory of Japan

The Graduate University for Advanced Studies (SOKENDAI)

K. Nakanishi

National Astronomical Observatory of Japan

The Graduate University for Advanced Studies (SOKENDAI)

D. S. Meier

New Mexico Institute of Mining and Technology

K. Wada

Kagoshima University

N. Kawakatu

National Institute of Technology, Kure College

T. Nakajima

Nagoya University

Astrophysical Journal Letters

2041-8205 (ISSN) 2041-8213 (eISSN)

Vol. 845 1 L5- L5


Astronomi, astrofysik och kosmologi


Onsala rymdobservatorium



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