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: Seyfert

galaxies: ISM

galaxies: active

galaxies: individual (NGC 1097)

Författare

T. Izumi

National Institutes of Natural Sciences - National Astronomical Observatory of Japan

K. Kohno

Research Center for the Early Universe

University of Tokyo

K. Fathi

Valhallav. 67

E. Hatziminaoglou

European Southern Observatory (ESO)

R. I. Davies

Max Planck-institutet

S. Martin

European Southern Observatory Santiago

Atacama Large Millimeter-submillimeter Array (ALMA)

S. Matsushita

Academia Sinica

E. Schinnerer

Max Planck-institutet

D. Espada

The Graduate University for Advanced Studies (SOKENDAI)

National Institutes of Natural Sciences - 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

The Graduate University for Advanced Studies (SOKENDAI)

National Institutes of Natural Sciences - National Astronomical Observatory of Japan

K. Nakanishi

The Graduate University for Advanced Studies (SOKENDAI)

National Institutes of Natural Sciences - National Astronomical Observatory of Japan

D. S. Meier

New Mexico Institute of Mining and Technology

K. Wada

Kagoshima University

N. Kawakatu

National Institute of Technology

T. Nakajima

Nagoya University

Astrophysical Journal Letters

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

Vol. 845 L5-

Ämneskategorier

Astronomi, astrofysik och kosmologi

Infrastruktur

Onsala rymdobservatorium

DOI

10.3847/2041-8213/aa808f