NGC 6860, Mrk 915, and MCG -01-24-012

II. Inflowing and outflowing cold molecular gas and the connection with ionized gas in Seyfert galaxies

¹ Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut, Mönchhofstr 12-14, D-69120 Heidelberg, Germany
² Departamento de Astronomia, Universidade Federal do Rio Grande do Sul, IF, CP 15051, 91501-970 Porto Alegre, RS, Brazil
³ Astronomy Department, Universidad de Concepción, Barrio Universitario S/N, Concepción 4030000, Chile
⁴ Observatorio Astronómico Nacional (OAN-IGN) - Observatorio de Madrid, Alfonso XII, 3, 28014 Madrid, Spain
⁵ Departamento de Física, CCNE, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS, Brazil
⁶ Centro de Astrobiología (CAB), CSIC-INTA, Ctra. de Ajalvir km 4, Torrejón de Ardoz, 28850 Madrid, Spain
⁷ Finnish Centre for Astronomy with ESO, University of Turku, 20014 Turku, Finland

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 25 April 2025
Accepted: 5 November 2025

Abstract

We present a study of the cold molecular gas kinematics in the inner ∼4–7 kpc (projected sizes) of three nearby Seyfert galaxies with active galactic nucleus (AGN) luminosities of ∼10⁴⁴ erg s⁻¹ using observations of the CO(2–1) emission line obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) at ∼0.5–0.8″ (∼150–400 pc) spatial resolutions. After modeling the CO profiles with multiple Gaussian components, we detected regions with double-peak profiles that exhibit kinematics distinct from the dominant rotational motion. In NGC 6860, a molecular outflow surrounding the bipolar emission of the [O III] ionized gas is observed extending up to R_out ∼ 560 pc from the nucleus. There is evidence of molecular inflows along the stellar bar, although an alternative scenario involving a decoupled rotation in a circumnuclear disk (CND) can also explain the observed kinematics. Mrk 915 shows double-peak CO profiles along one of its spiral arms. Due to the ambiguous orientation of its disk, part of the CO emission can be interpreted as a molecular gas inflow or an outflow reaching R_out ∼ 2.8 kpc. MCG -01-24-012 has double-peak profiles associated with a CND perpendicular to the [O III] bipolar emission. The CO in the CND is rotating while outflowing within R_out ∼ 3 kpc, with the disturbances possibly being caused by the passage of the ionized gas outflow. Overall, the mass inflow rates are larger than the accretion rate needed to produce the observed luminosities, suggesting that only a fraction of the inflowing gas ends up feeding the central black holes. Although we found signatures of AGN feedback on the cold molecular phase, the mass outflow rates of ∼0.09–3 M_⊙ yr⁻¹ indicate an overall weak impact at these AGN luminosities. Nonetheless, we may be witnessing the start of the depletion and ejection of the molecular gas reservoir that has accumulated over time.