ALMA Observations of the Physical and Chemical Conditions in Centaurus A
Artikel i vetenskaplig tidskrift, 2017

Centaurus A, with its gas-rich elliptical host galaxy, NGC 5128, is the nearest radio galaxy at a distance of 3.8 Mpc. Its proximity allows us to study the interaction among an active galactic nucleus, radio jets, and molecular gas in great detail. We present ALMA observations of low-J transitions of three CO isotopologues, HCN, HCO+, HNC, CN, and CCH toward the inner projected 500 pc of NGC 5128. Our observations resolve physical sizes down to 40 pc. By observing multiple chemical probes, we determine the physical and chemical conditions of the nuclear interstellar medium of NGC 5128. This region contains molecular arms associated with the dust lanes and a circumnuclear disk (CND) interior to the molecular arms. The CND is approximately 400 pc by 200 pc and appears to be chemically distinct from the molecular arms. It is dominated by dense gas tracers while the molecular arms are dominated by (CO)-C-12 and its rare isotopologues. The CND has a higher temperature, elevated CN/HCN and HCN/HNC intensity ratios, and much weaker (CO)-C-13 and (CO)-O-18 emission than the molecular arms. This suggests an influence from the AGN on the CND molecular gas. There is also absorption against the AGN with a low velocity complex near the systemic velocity and a high velocity complex shifted by about 60 km s(-1). We find similar chemical properties between the CND in emission and both the low and high velocity absorption complexes, implying that both likely originate from the CND. If the HV complex does originate in the CND, then that gas would correspond to gas falling toward the supermassive black hole.

galaxies: ISM


Centaurus A)

galaxies: elliptical and lenticular

galaxies: individual (NGC 5128

galaxies: structure

galaxies: active



M. McCoy

New Mexico Institute of Mining and Technology

J. Ott

National Radio Astronomy Observatory Socorro

D. S. Meier

National Radio Astronomy Observatory Socorro

New Mexico Institute of Mining and Technology

Sebastien Muller

Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium

D. Espada

Atacama Large Millimeter-submillimeter Array (ALMA)

The Graduate University for Advanced Studies (SOKENDAI)

National Astronomical Observatory of Japan

S. Martin

Atacama Large Millimeter-submillimeter Array (ALMA)

European Southern Observatory Santiago

F. P. Israel

Universiteit Leiden

C. Henkel


King Abdulaziz University

V. Impellizzeri

National Radio Astronomy Observatory

Atacama Large Millimeter-submillimeter Array (ALMA)

Susanne Aalto

Astronomi och plasmafysik

P. G. Edwards

Commonwealth Scientific and Industrial Research Organisation (CSIRO)

Andreas Brunthaler


N. Neumayer


A. B. Peck

National Radio Astronomy Observatory

P. van der Werf

Universiteit Leiden

I. Feain

The University of Sydney

Astrophysical Journal

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

Vol. 851 2 76


Astronomi, astrofysik och kosmologi



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