Nuclear molecular outflow in the Seyfert galaxy NGC 3227

¹ Centro de Astrobiología (CAB, CSIC-INTA), ESAC Campus, 28692 Villanueva de la Cañada, Madrid, Spain
e-mail: aalonsol@cab.inta-csic.es
² Observatorio de Madrid, OAN-IGN, Alfonso XII, 3, 28014 Madrid, Spain
³ Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH, UK
⁴ Max Planck Institut für Extraterrestrische Physik, Postfach 1312 85741 Garching bei München, Germany
⁵ LERMA, Obs. de Paris, PSL Research Univ., Collége de France, CNRS, Sorbonne Univ., UPMC, Paris, France
⁶ DARK, The Niels Bohr Institute, University of Copenhagen, Vibenshuset, Lyngbyvej 2, 2100 Copenhagen Ø, Denmark
⁷ Steward Observatory, University of Arizona, 933 N. Cherry Avenue, Tucson, AZ, USA
⁸ Núcleo de Astronomía de la Facultad de Ingeniería, Universidad Diego Portales, Av. Ejército Libertador 441, Santiago, Chile
⁹ Department of Physics & Astronomy, University of Southampton, Hampshire SO17 1BJ, Southampton, UK
¹⁰ Instituto de Física de Cantabria, CSIC-Universidad de Cantabria, 39005 Santander, Spain
¹¹ Department of Physics & Astronomy, University of Alaska Anchorage 99508-4664, USA
¹² INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
¹³ National Astronomical Observatory of Japan, National Institutes of Natural Sciences (NINS), 2-21-1 Osawa, Mitaka, Tokyo 181–8588, Japan
¹⁴ Department of Astronomical Science, SOKENDAI (The Graduate University of Advanced Studies), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
¹⁵ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
¹⁶ Astrophysics Research Institute, Liverpool John Moores University, IC2 Liverpool Science Park, 146, Brownlow Hill L3 5RF, UK
¹⁷ Department of Physics and Astronomy, University of Texas at San Antonio, 1 UTSA Circle, San Antonio, TX 78249, USA
¹⁸ Instituto de Astrofísica de Canarias, Calle Vía Láctea, s/n, 38205 La Laguna, Tenerife, Spain
¹⁹ Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
²⁰ Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, PR China
²¹ Centre for Extragalactic Astronomy, Durham University, South Road, Durham DH1 3LE, UK
²² Excellence Cluster Origins, Ludwig-Maximilians-Universität München, Boltzmannstr. 2, 85748 Garching, Germany

Received: 8 March 2019
Accepted: 12 June 2019

Abstract

ALMA observations have revealed nuclear dusty molecular disks or tori with characteristic sizes 15−40 pc in the few Seyferts and low -luminosity AGN that have been studied so far. These structures are generally decoupled both morphologically and kinematically from the host galaxy disk. We present ALMA observations of the CO(2–1) and CO(3–2) molecular gas transitions and associated (sub-) millimeter continua of the nearby Seyfert 1.5 galaxy NGC 3227 with angular resolutions 0.085 − 0.21″ (7–15 pc). On large scales, the cold molecular gas shows circular motions as well as streaming motions on scales of a few hundred parsecs that are associated with a large-scale bar. We fit the nuclear ALMA 1.3 mm emission with an unresolved component and an extended component. The 850 μm emission shows at least two extended components, one along the major axis of the nuclear disk, and the other along the axis of the ionization cone. The molecular gas in the central region (1″ ∼ 73 pc) shows several CO clumps with complex kinematics that appears to be dominated by noncircular motions. While we cannot conclusively demonstrate the presence of a warped nuclear disk, we also detected noncircular motions along the kinematic minor axis. They reach line-of-sight velocities of v − v_sys = 150 − 200 km s⁻¹. Assuming that the radial motions are in the plane of the galaxy, we interpret them as a nuclear molecular outflow due to molecular gas in the host galaxy that is entrained by the AGN wind. We derive molecular outflow rates of 5 M_⊙ yr⁻¹ and 0.6 M_⊙ yr⁻¹ at projected distances of up to 30 pc to the northeast and southwest of the AGN, respectively. At the AGN location we estimate a mass in molecular gas of 5 × 10⁵ M_⊙ and an equivalent average column density N(H₂) = 2 − 3 × 10²³ cm⁻² in the inner 15 pc. The nuclear CO(2–1) and CO(3–2) molecular gas and submillimeter continuum emission of NGC 3227 do not resemble the classical compact torus. Rather, these emissions extend for several tens of parsecs and appear connected with the circumnuclear ring in the host galaxy disk, as found in other local AGN.