Molecular line emission in NGC 1068 imaged with ALMA : I. An AGN-driven outflow in the dense molecular gas
Artikel i vetenskaplig tidskrift, 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: nuclei

Galaxies: individual: NGC 1068

Radio lines: galaxies

Galaxies: Seyfert

Galaxies: ISM

Galaxies: kinematics and dynamics


S. G. Burillo

Observatorio Astronomico Nacional

F. Combes

CNRS Centre National de la Recherche Scientifique

A. Usero

Observatorio Astronomico Nacional

Susanne Aalto

Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik

M. Krips

Université Grenoble Alpes

S. Viti

University College London (UCL)

A. Alonso-Herrero

CSIC-UC - Instituto de Física de Cantabria (IFCA)

L. K. Hunt

Osservatorio Astrofisico di Arcetri

E. Schinnerer

Max Planck-institutet

A. J. Baker

Rutgers, The State University of New Jersey

F. Boone

Universite de Toulouse

V. Casasola

Istituto di Radioastronomia

L. Colina

CSIC-INTA - Centro de Astrobiologia (CAB)

Francesco Costagliola

CSIC - Instituto de Astrofísica de Andalucía (IAA)

A. Eckart

Universität zu Köln

A. Fuente

Observatorio Astronomico Nacional

C. Henkel

Max Planck-institutet

King Aldulaziz University

A. Labiano

Eidgenössische Technische Hochschule Zürich (ETH)

Observatorio Astronomico Nacional

S. Martín

Université Grenoble Alpes

I. Márquez

CSIC - Instituto de Astrofísica de Andalucía (IAA)

Sebastien Muller

Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium

P. Planesas

Observatorio Astronomico Nacional

C. Ramos Almeida

Instituto Astrofisico de Canarias

Universidad de la Laguna

M. Spaans

Rijksuniversiteit Groningen

L. J. Tacconi

Max Planck-institutet

P.P. van der Werf

Universiteit Leiden

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 567 125- A125




Onsala rymdobservatorium