Volume 580, August 2015
|Number of page(s)||21|
|Published online||23 July 2015|
High-resolution imaging of the molecular outflows in two mergers: IRAS 17208-0014 and NGC 1614⋆
Observatorio Astronómico Nacional (OAN-IGN)-Observatorio de
Madrid, Alfonso XII,
2 Observatoire de Paris, LERMA, CNRS, 61 av. de l’Observatoire, 75014 Paris, France
3 Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Observatory, 439 94 Onsala, Sweden
4 Centro de Astrobiología (CSIC-INTA), Ctra de Torrejón a Ajalvir, km 4, 28850 Torrejón de Ardoz, Madrid, Spain
5 ASTRO-UAM, Universidad Autónoma de Madrid (UAM), Unidad Asociada CSIC, 28049 Madrid, Spain
6 Instituto de Física de Cantabria, CSIC-UC, 39005 Santander, Spain
7 INAF-Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy
8 Instituto de Astrofísica de Andalucía (CSIC), Apdo 3004, 18080 Granada, Spain
9 Institute for Astronomy, Department of Physics, ETH Zurich, 8093 Zurich, Switzerland
10 Institut de Radio Astronomie Millimétrique (IRAM), 300 rue de la Piscine, Domaine universitaire de Grenoble, 38406 St. Martin d’Hères, France
11 Max-Planck-Institut für extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany
12 Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
Received: 18 March 2015
Accepted: 19 May 2015
Context. Galaxy evolution scenarios predict that the feedback of star formation and nuclear activity (AGN) can drive the transformation of gas-rich spiral mergers into (ultra) luminous infrared galaxies and, eventually, lead to the build-up of QSO/elliptical hosts.
Aims. We study the role that star formation and AGN feedback have in launching and maintaining the molecular outflows in two starburst-dominated advanced mergers, NGC 1614 (DL = 66 Mpc) and IRAS 17208-0014 (DL = 181 Mpc), by analyzing the distribution and kinematics of their molecular gas reservoirs. Both galaxies present evidence of outflows in other phases of their ISM.
Methods. We used the Plateau de Bure interferometer (PdBI) to image the CO(1–0) and CO(2–1) line emissions in NGC 1614 and IRAS 17208-0014, respectively, with high spatial resolution (0''̣5–1''̣2). The velocity fields of the gas were analyzed and modeled to find the evidence of molecular outflows in these sources and characterize the mass, momentum, and energy of these components.
Results. While most (≥95%) of the CO emission stems from spatially resolved (~2−3 kpc-diameter) rotating disks, we also detect in both mergers the emission from high-velocity line wings that extend up to ±500–700 km s-1, well beyond the estimated virial range associated with rotation and turbulence. The kinematic major axis of the line-wing emission is tilted by ~90° in NGC 1614 and by ~180° in IRAS 17208-0014 relative to the major axes of their respective rotating disks. These results can be explained by the existence of non-coplanar molecular outflows in both systems: the outflow axis is nearly perpendicular to the rotating disk in NGC 1614, but it is tilted relative to the angular momentum axis of the rotating disk in IRAS 17208-0014.
Conclusions. In stark contrast to NGC 1614, where star formation alone can drive its molecular outflow, the mass, energy, and momentum budget requirements of the molecular outflow in IRAS 17208-0014 can be best accounted for by the existence of a so far undetected (hidden) AGN of LAGN ~ 7 × 1011 L⊙. The geometry of the molecular outflow in IRAS 17208-0014 suggests that the outflow is launched by a non-coplanar disk that may be associated with a buried AGN in the western nucleus.
Key words: galaxies: individual: IRAS 17208-0014 / galaxies: ISM / galaxies: kinematics and dynamics / galaxies: starburst / galaxies: nuclei / galaxies: individual: NGC1614
© ESO, 2015
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