Disentangling the Circumnuclear Environs of Centaurus A. III. An Inner Molecular Ring, Nuclear Shocks, and the CO to Warm H-2 Interface
Artikel i vetenskaplig tidskrift, 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

galaxies: individual (NGC 5128)

galaxies: structure

ISM: molecules



D. Espada

National Institutes of Natural Sciences - National Astronomical Observatory of Japan

The Graduate University for Advanced Studies (SOKENDAI)

Atacama Large Millimeter-submillimeter Array (ALMA)

S. Matsushita

Academia Sinica

R.E. Miura

National Institutes of Natural Sciences - National Astronomical Observatory of Japan

F.P. Israel

Universiteit Leiden

N. Neumayer

Max Planck-institutet

S. Martin

European Southern Observatory Santiago

Atacama Large Millimeter-submillimeter Array (ALMA)

C. Henkel

Max Planck-institutet

King Abdulaziz University

T. Izumi

University of Tokyo

D. Iono

The Graduate University for Advanced Studies (SOKENDAI)

National Institutes of Natural Sciences - National Astronomical Observatory of Japan

Susanne Aalto

Astronomi och plasmafysik

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. 843 136


Astronomi, astrofysik och kosmologi