ALMA Observations of the Physical and Chemical Conditions in Centaurus A
Journal article, 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.
Centaurus A)
galaxies: structure
galaxies: elliptical and lenticular
galaxies: active
galaxies: individual (NGC 5128
galaxies: ISM
astrochemistry
cD
Author
M. McCoy
New Mexico Institute of Mining and Technology
J. Ott
National Radio Astronomy Observatory
D. S. Meier
National Radio Astronomy Observatory
New Mexico Institute of Mining and Technology
Sebastien Muller
Chalmers, Earth and Space Sciences, Onsala Space Observatory
D. Espada
The Graduate University for Advanced Studies (SOKENDAI)
Atacama Large Millimeter-submillimeter Array (ALMA)
National Astronomical Observatory of Japan
S. Martin
Atacama Large Millimeter-submillimeter Array (ALMA)
European Southern Observatory Santiago
F. P. Israel
Leiden University
C. Henkel
King Abdulaziz University
Max Planck Society
V. Impellizzeri
National Radio Astronomy Observatory
Atacama Large Millimeter-submillimeter Array (ALMA)
Susanne Aalto
Astronomy and Plasmaphysics
P. G. Edwards
Commonwealth Scientific and Industrial Research Organisation (CSIRO)
Andreas Brunthaler
Max Planck Society
N. Neumayer
Max Planck Society
A. B. Peck
National Radio Astronomy Observatory
P. van der Werf
Leiden University
I. Feain
The University of Sydney
Astrophysical Journal
0004-637X (ISSN) 1538-4357 (eISSN)
Vol. 851 2 76Subject Categories (SSIF 2011)
Astronomy, Astrophysics and Cosmology
DOI
10.3847/1538-4357/aa99d6