AGN feedback in action in the molecular gas ring of the Seyfert galaxy NGC 7172

¹ Centro de Astrobiología (CAB), CSIC-INTA, Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain
e-mail: aalonso@cab.inta-csic.es
² Observatorio de Madrid, OAN-IGN, Alfonso XII, 3, 28014 Madrid, Spain
³ Instituto de Física Fundamental, CSIC, Calle Serrano 123, 28006 Madrid, Spain
⁴ Max-Planck-Institut für Extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany
⁵ LERMA, Observatoire de Paris, Collège de France, PSL University, CNRS, Sorbonne University, Paris, France
⁶ Department of Physics & Astronomy, University of Alaska Anchorage, Anchorage, AK 99508-4664, USA
⁷ Instituto de Astrofísica de Canarias, Calle Vía Láctea s/n, 38205 La Laguna, Tenerife, Spain
⁸ Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
⁹ Department of Physics, University of Oxford, Oxford OX1 3RH, UK
¹⁰ School of Physics & Astronomy, University of Southampton, Southampton, SO17 1BJ Hampshire, UK
¹¹ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
¹² The University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249, USA
¹³ National Astronomical Observatory of Japan, National Institutes of Natural Sciences (NINS), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
¹⁴ Departamento de Física de la Tierra y Astrofísica, Fac. de CC Físicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
¹⁵ Instituto de Física de Partículas y del Cosmos IPARCOS, Fac. CC Físicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
¹⁶ INAF – Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy
¹⁷ Department of Astronomy, School of Science, Graduate University for Advanced Studies (SOKENDAI), Mitaka, Tokyo 181-8588, Japan
¹⁸ Núcleo de Astronomía de la Facultad de Ingeniería, Universidad Diego Portales, Av. Ejército Libertador 441, Santiago, Chile
¹⁹ Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, PR China

Received: 3 February 2023
Accepted: 22 May 2023

Abstract

We present new ALMA observations of the CO(3−2) transition and associated 854 μm continuum at 0.06 − 0.3″ resolution, together with new VLT/SINFONI observations of NGC 7172. This is a luminous (bolometric luminosity of ≃10⁴⁴ erg s⁻¹) Seyfert galaxy that belongs to the Galaxy Activity, Torus, and Outflow Survey (GATOS). The ALMA CO(3−2) observations reveal the presence of a highly inclined cold molecular gas ring with an approximate radius of 3 − 4″ ≃ 540 − 720 pc, which is likely associated with an inner Lindblad resonance of a putative stellar bar. There are noncircular motions in the VLT/SINFONI [Si VI]λ1.96 μm and H₂ at 2.12 μm, and ALMA CO(3−2) velocity fields. After subtracting the stellar velocity field, we detected [Si VI] blueshifted velocities of a few hundred km s⁻¹ to the south of the active galactic nucleus (AGN) position. They trace outflowing ionized gas outside the plane of the galaxy and out to projected distances of ≃200 pc. The CO(3−2) position-velocity diagram along the kinematic minor axis displays noncircular motions with observed velocities of up to ∼150 km s⁻¹. Assuming that these are taking place in the disk of the galaxy, the observed velocity signs imply that the molecular gas ring is not only rotating but also outflowing. We derived an integrated cold molecular gas mass outflow rate of ∼40 M_⊙ yr⁻¹ for the ring. Using the ALMA 854 μm extended emission map, we resolved a 32 pc radius torus with a gas mass of 8 × 10⁵ M_⊙. These torus properties are similar to other Seyfert galaxies in the GATOS sample. We measured a decreased cold molecular gas concentration in the nuclear-torus region relative to the circumnuclear region when compared to other less luminous Seyfert galaxies. We conclude that the effects of AGN feedback in NGC 7172, which are likely caused by the AGN wind and/or the moderate luminosity radio jet, are seen as a large-scale outflowing molecular gas ring and accompanying redistribution of molecular gas in the nuclear regions.