Disentangling the Circumnuclear Environs of Centaurus A. III. An Inner Molecular Ring, Nuclear Shocks, and the CO to Warm H-2 Interface
Journal article, 2017

We present the distribution and kinematics of the molecular gas in the circumnuclear disk (CND; 400 pc ×200 pc) of Centaurus A with resolutions of ∼5 pc (0.″3) and shed light onto the mechanism feeding the active galactic nucleus (AGN) using CO(3-2), HCO + (4-3), HCN(4-3), and CO(6-5) observations obtained with ALMA. Multiple filaments or streamers of tens to a hundred parsec scale exist within the CND, which form a ring-like structure with an unprojected diameter of 9″ ×6″ (162 pc ×108 pc) and a position angle P.A. ≃ 155°. Inside the nuclear ring, there are two leading and straight filamentary structures with lengths of about 30-60 pc at P.A. ≃ 120° on opposite sides of the AGN, with a rotational symmetry of 180° and steeper position-velocity diagrams, which are interpreted as nuclear shocks due to non-circular motions. Along the filaments, and unlike other nearby AGNs, several dense molecular clumps present low HCN/HCO + (4-3) ratios (≲0.5). The filaments abruptly end in the probed transitions at r ≃ 20 pc from the AGN, but previous near-IR H 2 (J = 1-0)S(1) maps show that they continue in an even warmer gas phase (T ∼ 1000 K), winding up in the form of nuclear spirals, and forming an inner ring structure with another set of symmetric filaments along the N-S direction and within r ≃ 10 pc. The molecular gas is governed primarily by non-circular motions, being the successive shock fronts at different scales where loss of angular momentum occurs, a mechanism that may feed efficiently powerful radio galaxies down to parsec scales.


galaxies: elliptical and lenticular

ISM: molecules

galaxies: individual (NGC 5128)

galaxies: structure


D. Espada

Atacama Large Millimeter-submillimeter Array (ALMA)

National Astronomical Observatory of Japan

The Graduate University for Advanced Studies (SOKENDAI)

S. Matsushita

Academia Sinica

R.E. Miura

National Astronomical Observatory of Japan

F.P. Israel

Leiden University

N. Neumayer

Max Planck Society

S. Martin

European Southern Observatory Santiago

Atacama Large Millimeter-submillimeter Array (ALMA)

C. Henkel

King Abdulaziz University

Max Planck Society

T. Izumi

University of Tokyo

D. Iono

The Graduate University for Advanced Studies (SOKENDAI)

National Astronomical Observatory of Japan

Susanne Aalto

Astronomy and Plasmaphysics

J. Ott

National Radio Astronomy Observatory Socorro

A.B. Peck

Gemini Observatory North

A.C. Quillen

University of Rochester

K. Kohno

University of Tokyo

Astrophysical Journal

0004-637X (ISSN) 1538-4357 (eISSN)

Vol. 843 2 136

Subject Categories

Astronomy, Astrophysics and Cosmology



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