ALMA resolves the remarkable molecular jet and rotating wind in the extremely radio-quiet galaxy NGC 1377

Springer Link (Chiba Institute of Technology)

Abstract

Submillimetre and millimetre line and continuum observations are important in probing the morphology, column density, and dynamics of the molecular gas and dust around obscured active galactic nuclei (AGNs) and their mechanical feedback. With very high-resolution (0.'' 02x0.'' 03 (2x3 pc)) ALMA 345 GHz observations of CO 3-2, HCO+ 4-3, vibrationally excited HCN 4-3 nu (2)=1f, and continuum we have studied the remarkable, extremely radio-quiet, molecular jet and wind of the lenticular galaxy NGC 1377. The outflow structure is resolved, revealing a 150 pc long, clumpy, high-velocity (similar to 600 km s(-1)), collimated molecular jet where the molecular emission is emerging from the spine of the jet with an average diameter of 3-7 pc. The jet widens to 10-15 pc about 25 pc from the centre, which is possibly due to jet-wind interactions. A narrow-angle (50 degrees -70 degrees), misaligned and rotating molecular wind surrounds the jet, and both are enveloped by a larger-scale CO-emitting structure at near-systemic velocity. The jet and narrow wind have steep radial gas excitation gradients and appear turbulent with high gas dispersion (sigma> 40 km s(-1)). The jet shows velocity reversals that we propose are caused by precession, or more episodic directional changes. We discuss the mechanisms powering the outflow, and we find that an important process for the molecular jet and narrow wind is likely magneto-centrifugal driving. In contrast, the large-scale CO-envelope may be a slow wind, or cocoon that stems from jet-wind interactions. An asymmetric, nuclear r similar to 2 pc dust structure with a high inferred molecular column density N(H-2) similar or equal to 1.8x10(24) cm(-2) is detected in continuum and also shows compact emission from vibrationally excited HCN. The nuclear dust emission is hot (T-d> 180 K) and its luminosity is likely powered by a buried AGN. The lopsided structure appears to be a warped disk, which is responsible for a significant part of the nuclear obscuration and possibly formed as a result of uneven gas inflows. The dynamical mass inside r=1.4 pc is estimated to9(-3)(+2) x 10(6)M(circle dot)9- 3+ 2x10 6M circle dot, implying that the supermassive black hole (SMBH) has a high mass with respect to the stellar velocity dispersion of NGC 1377. We suggest that the SMBH of NGC 1377 is currently in a state of moderate growth, at the end of a more intense phase of accretion and also evolving from a state of more extreme nuclear obscuration. The nuclear growth may be fuelled by low-angular momentum gas inflowing from the gas ejected in the molecular jet and wind. Such a feedback-loop of cyclic outflows and central accretion could explain why there is still a significant reservoir of molecular gas in this ageing, lenticular galaxy. A feedback-loop would be an effective process in growing the nuclear SMBH and thus would constitute an important phase in the evolution of NGC 1377. This also invites new questions as to SMBH growth processes in obscured, dusty galaxies.

Authors 17

1. S. Aalto

   Chalmers University of Technology

   Affiliation as printed

   Department of Space, Earth and Environment, Onsala Space Observatory, Chalmers University of Technology, 439 92 Onsala, Sweden

2. N. Falstad

   Chalmers University of Technology

   Affiliation as printed

   Department of Space, Earth and Environment, Onsala Space Observatory, Chalmers University of Technology, 439 92 Onsala, Sweden

3. S. Muller

   Chalmers University of Technology

   Affiliation as printed

   Department of Space, Earth and Environment, Onsala Space Observatory, Chalmers University of Technology, 439 92 Onsala, Sweden

4. Keiichi Wada

   Kagoshima University

   Affiliation as printed

   Kagoshima University, Kagoshima 890-0065, Japan

5. J. S. Gallagher

   University of Wisconsin–Madison

   Affiliation as printed

   Department of Astronomy, University of Wisconsin-Madison, 5534 Sterling, 475 North Charter Street, Madison, WI 53706, USA

6. S. König

   Chalmers University of Technology

   Affiliation as printed

   Department of Space, Earth and Environment, Onsala Space Observatory, Chalmers University of Technology, 439 92 Onsala, Sweden

7. Kazushi Sakamoto

   Institute of Astronomy and Astrophysics, Academia Sinica

   Affiliation as printed

   Institute of Astronomy and Astrophysics, Academia Sinica, PO Box 23-141, 10617 Taipei, Taiwan

8. W. H. T. Vlemmings

   Chalmers University of Technology

   Affiliation as printed

   Department of Space, Earth and Environment, Onsala Space Observatory, Chalmers University of Technology, 439 92 Onsala, Sweden

9. Chiara Ceccobello

   Chalmers University of Technology

   Affiliation as printed

   Department of Space, Earth and Environment, Onsala Space Observatory, Chalmers University of Technology, 439 92 Onsala, Sweden

10. K. M. Dasyra

    National and Kapodistrian University of Athens

    Affiliation as printed

    Department of Astrophysics, Astronomy & Mechanics, Faculty of Physics, University of Athens, Panepistimiopolis Zografos 15784, Greece

11. Françoise Combes

    Centre National de la Recherche Scientifique · Collège de France · Université Paris Sciences et Lettres · Observatoire de Paris · Sorbonne Université · Laboratoire d’Etudes du Rayonnement et de la Matière en Astrophysique et Atmosphères

    Affiliation as printed

    Observatoire de Paris, Collège de France, PSL University, Sorbonne University, LERMA, CNRS, Paris, France

12. S. García‐Burillo

    Spanish National Observatory

    Affiliation as printed

    Observatorio Astronómico Nacional (OAN)-Observatorio de Madrid, Alfonso XII 3, 28014 Madrid, Spain

13. Yoko Oya

    The University of Tokyo

    Affiliation as printed

    Department of Physics, The University of Tokyo 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan

14. S. Martín

    Atacama Large Millimeter Submillimeter Array · European Southern Observatory

    Affiliation as printed

    European Southern Observatory, Alonso de Córdova 3107, Vitacura, Santiago 763-0355, Chile

    Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura, Santiago 763-0355, Chile

15. Paul P. van der Werf Aachen Leiden Observatory

    Leiden University · Leiden Observatory

    Affiliation as printed

    Leiden Observatory, Leiden University, 2300 RA Leiden, The Netherlands

16. Aaron S. Evans

    National Radio Astronomy Observatory · University of Virginia

    Affiliation as printed

    University of Virginia, Charlottesville, VA 22904, USA, NRAO, 520 Edgemont Road, Charlottesville, VA 22903, USA

17. Jari K. Kotilainen

    University of Turku

    Affiliation as printed

    Finnish Centre for Astronomy with ESO (FINCA), University of Turku Quantum, Vesilinnantie 5, 20014 Turku, Finland