Issue |
A&A
Volume 590, June 2016
|
|
---|---|---|
Article Number | A73 | |
Number of page(s) | 12 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/201527664 | |
Published online | 13 May 2016 |
A precessing molecular jet signaling an obscured, growing supermassive black hole in NGC 1377?⋆,⋆⋆
1
Department of Earth and Space SciencesChalmers University of Technology,
Onsala Observatory, 439
92
Onsala, Sweden
e-mail: saalto@chalmers.se
2
Institute of Astronomy and Astrophysics, Academia
Sinica, PO Box
23-141, 10617
Taipei,
Taiwan
3
Department of Astronomy, University of
Wisconsin-Madison, 5534 Sterling,
475 North Charter Street, Madison
WI
53706,
USA
4
Department of Astrophysics, Astronomy & Mechanics, Faculty
of Physics, University of Athens, 15784
Panepistimiopolis Zografos,
Greece
5
Kagoshima University, 890-0065
Kagoshima,
Japan
6
Observatoire de Paris, LERMA (CNRS: UMR 8112),
61 Av. de l’Observatoire,
75014
Paris,
France
7
Observatorio Astronómico Nacional (OAN) - Observatorio de
Madrid, Alfonso XII
3, 28014
Madrid,
Spain
8
Harvard-Smithsonian Center for Astrophysics,
60 Garden Street, Cambridge, MA
02138,
USA
9
European Southern Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile
10
Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile
11
Institut de Radio Astronomie Millimétrique (IRAM), 300 rue de la
Piscine, Domaine Universitaire de Grenoble, 38406St.
Martin d′Hères, France
12
Leiden Observatory, Leiden University,
2300 RA, Leiden, The
Netherlands
13
University of Virginia, Charlottesville, VA 22904, USA, NRAO, 520 Edgemont
Road, Charlottesville, VA
22903,
USA
14
Finnish Centre for Astronomy with ESO (FINCA), University of
Turku, Väisäläntie
20, 21500
Kaarina,
Finland
Received:
29
October
2015
Accepted:
23
February
2016
With high resolution (0.̋25 × 0.̋18) ALMA CO 3−2 (345 GHz) observations of the nearby (D = 21 Mpc, 1′′ = 102 pc), extremely radio-quiet galaxy NGC 1377, we have discovered a high-velocity, very collimated nuclear outflow which we interpret as a molecular jet with a projected length of ±150 pc. The launch region is unresolved and lies inside a radius r< 10 pc. Along the jet axis we find strong velocity reversals where the projected velocity swings from −150km s-1 to +150 km s-1. A simple model of a molecular jet precessing around an axis close to the plane of the sky can reproduce the observations. The velocity of the outflowing gas is difficult to constrain due to the velocity reversals but we estimate it to be between 240 and 850 km s-1 and the jet to precess with a period P = 0.3−1.1 Myr. The CO emission is clumpy along the jet and the total molecular mass in the high-velocity (±(60 to 150 km s-1)) gas lies between 2 × 106M⊙ (light jet) and 2 × 107M⊙ (massive jet). There is also CO emission extending along the minor axis of NGC 1377. It holds > 40% of the flux in NGC 1377 and may be a slower, wide-angle molecular outflow which is partially entrained by the molecular jet. We discuss the driving mechanism of the molecular jet and suggest that it is either powered by a (faint) radio jet or by an accretion disk-wind similar to those found towards protostars. It seems unlikely that a massive jet could have been driven out by the current level of nuclear activity which should then have undergone rapid quenching. The light jet would only have expelled 10% of the inner gas and may facilitate nuclear activity instead of suppressing it. The nucleus of NGC 1377 harbours intense embedded activity and we detect emission from vibrationally excited HCN J = 4−3ν2 = 1f which is consistent with hot gas and dust. We find large columns of H2 in the centre of NGC 1377 which may be a sign of a high rate of recent gas infall. The dynamical age ofthe molecular jet is short (<1 Myr), which could imply that it is young and consistent with the notion that NGC 1377 is caught in a transient phase of its evolution. However, further studies are required to determine the age of the molecular jet, its mass and the role it is playing in the growth of the nucleus of NGC 1377.
Key words: galaxies: evolution / galaxies: active / galaxies: individual: NGC 1377 / galaxies: jets / galaxies: ISM / ISM: molecules
Based on observations carried out with the ALMA Interferometer. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada) and NSC and ASIAA (Taiwan), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ.
FITS files of the reduced data cubes are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/590/A73
© ESO, 2016
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