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: structure


galaxies: individual (NGC 5128

galaxies: ISM

Centaurus A)

galaxies: active

galaxies: elliptical and lenticular


M. McCoy

New Mexico Institute of Mining and Technology

J. Ott

National Radio Astronomy Observatory Socorro

D. S. Meier

New Mexico Institute of Mining and Technology

National Radio Astronomy Observatory Socorro

Sebastien Muller

Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium

D. Espada

The Graduate University for Advanced Studies (SOKENDAI)

Atacama Large Millimeter-submillimeter Array (ALMA)

National Institutes of Natural Sciences - National Astronomical Observatory of Japan

S. Martin

European Southern Observatory Santiago

Atacama Large Millimeter-submillimeter Array (ALMA)

F. P. Israel

Universiteit Leiden

C. Henkel

King Abdulaziz University

Max Planck-institutet

V. Impellizzeri

Atacama Large Millimeter-submillimeter Array (ALMA)

National Radio Astronomy Observatory

Susanne Aalto

Astronomi och plasmafysik

P. G. Edwards

Commonwealth Scientific and Industrial Research Organization

Andreas Brunthaler

Max Planck-institutet

N. Neumayer

Max Planck-institutet

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 76


Astronomi, astrofysik och kosmologi