Molecular line emission in NGC 1068 imaged with ALMA : I. An AGN-driven outflow in the dense molecular gas
Journal article, 2014
Aims. We investigate the fueling and the feedback of star formation and nuclear activity in NGC 1068, a nearby (D = 14 Mpc) Seyfert 2 barred galaxy, by analyzing the distribution and kinematics of the molecular gas in the disk. We aim to understand if and how gas accretion can self-regulate.Methods. We have used the Atacama Large Millimeter Array (ALMA) to map the emission of a set of dense molecular gas (n(H2) ' 1056 cm3) tracers (CO(3-2), CO(6-5), HCN(4-3), HCO+(4-3), and CS(7-6)) and their underlying continuum emission in the central r ∼ 2 kpc of NGC 1068 with spatial resolutions ∼0:3000:500 (∼20-35 pc for the assumed distance of D = 14 Mpc). Results. The sensitivity and spatial resolution of ALMA give an unprecedented detailed view of the distribution and kinematics of the dense molecular gas (n(H2) ≈ 1056cm3) in NGC 1068. Molecular line and dust continuum emissions are detected from a r ∼ 200 pc off-centered circumnuclear disk (CND), from the 2.6 kpc-diameter bar region, and from the r ∼ 1:3 kpc starburst (SB) ring. Most of the emission in HCO+, HCN, and CS stems from the CND. Molecular line ratios show dramatic order-of-magnitude changes inside the CND that are correlated with the UV/X-ray illumination by the active galactic nucleus (AGN), betraying ongoing feedback. We used the dust continuum fluxes measured by ALMA together with NIR/MIR data to constrain the properties of the putative torus using CLUMPY models and found a torus radius of 20+6 10 pc. The Fourier decomposition of the gas velocity field indicates that rotation is perturbed by an inward radial flow in the SB ring and the bar region. However, the gas kinematics from r ∼ 50 pc out to r ∼ 400 pc reveal a massive (Mmol ∼ 2:7+0:9 1:2 × 107 M) outflow in all molecular tracers. The tight correlation between the ionized gas outflow, the radio jet, and the occurrence of outward motions in the disk suggests that the outflow is AGN driven. Conclusions. The molecular outflow is likely launched when the ionization cone of the narrow line region sweeps the nuclear disk. The outflow rate estimated in the CND, dM=dt ∼ 63+21 37 M yr1, is an order of magnitude higher than the star formation rate at these radii, confirming that the outflow is AGN driven. The power of the AGN is able to account for the estimated momentum and kinetic luminosity of the outflow. The CND mass load rate of the CND outflow implies a very short gas depletion timescale of ≤1 Myr. The CND gas reservoir is likely replenished on longer timescales by efficient gas inflow from the outer disk. © ESO 2014.
Galaxies: individual: NGC 1068
Galaxies: nuclei
Galaxies: ISM
Radio lines: galaxies
Galaxies: kinematics and dynamics
Galaxies: Seyfert
Author
S. G. Burillo
Observatorio Astronomico Nacional
F. Combes
CNRS Centre National de la Recherche Scientifique
A. Usero
Observatorio Astronomico Nacional
Susanne Aalto
Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics
M. Krips
Universite Grenoble Alpes
S. Viti
UCL
A. Alonso-Herrero
CSIC-UC - Instituto de Física de Cantabria (IFCA)
L. K. Hunt
Osservatorio Astrofisico Di Arcetri
E. Schinnerer
Max Planck Institut fur Astronomie
A. J. Baker
Rutgers, The State University of New Jersey
F. Boone
Universite de Toulouse
V. Casasola
Istituto Di Radioastronomia, Bologna
L. Colina
CSIC-INTA - Centro de Astrobiologia (CAB)
Francesco Costagliola
CSIC - Instituto de Astrofísica de Andalucía (IAA)
A. Eckart
Universitat zu Koln
A. Fuente
Observatorio Astronomico Nacional
C. Henkel
King Aldulaziz University
Max Planck Institut fur Radioastronomie
A. Labiano
ETH Zurich
Observatorio Astronomico Nacional
S. Martín
Universite Grenoble Alpes
I. Márquez
CSIC - Instituto de Astrofísica de Andalucía (IAA)
Sebastien Muller
Chalmers, Earth and Space Sciences, Onsala Space Observatory
P. Planesas
Observatorio Astronomico Nacional
C. Ramos Almeida
Universidad de la Laguna
Instituto Astrofisico de Canarias
M. Spaans
University of Groningen, Kapteyn Astronomical Institute
L. J. Tacconi
Max Planck Institut fur extraterrestrische Physik
P.P. van der Werf
Leiden Observatory Research Institute
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 567 125- A125Subject Categories (SSIF 2011)
Physical Sciences
Infrastructure
Onsala Space Observatory
DOI
10.1051/0004-6361/201423843