ALMA observations of CS in NGC 1068: chemistry and excitation
Journal article, 2020
We present results from Atacama Large Millimeter/submillimeter Array (ALMA) observations of CS from the nearby galaxy NGC 1068 (similar to 14 Mpc). This Seyfert 2 barred galaxy possesses a circumnuclear disc (CND, r similar to 200 pc) and a starburst ring (SB ring, r similar to 1.3 kpc). These high-resolution maps (similar to 0.5 arcsec, similar to 35 pc) allow us to analyse specific sub-regions in the galaxy and investigate differences in line intensity ratios and physical conditions, particularly those between the CND and SB ring. Local thermodynamic equilibrium (LTE) analysis of the gas is used to calculate CS densities in each sub-region, followed by the non-LTE analysis conducted using the radiative transfer code RADEX to fit observations and constrain gas temperature, CS column density and hydrogen density. Finally, the chemical code UCLCHEM is used to reconstruct the gas, allowing an insight into its origin and chemical history. The density of hydrogen in the CND is found to be >= 10(5) cm(-2), although exact values vary, reaching 10(6) cm(-2) at the active galactic nucleus. The conditions in the two arms of the SB ring appear similar to one another, though the density found (similar to 10(4) cm(-2)) is lower than in the CND. The temperature in the CND increases from east to west, and is also overall greater than found in the SB ring. These modelling methods indicate the requirement for multiphase gas components in order to fit the observed emission over the galaxy. A larger number of high-resolution transitions across the SLED may allow for further constraining of the conditions, particularly in the SB ring.
radio lines: galaxies
galaxies: nuclei
galaxies: ISM
galaxies: individual: NGC 1068
Author
M. Scourfield
University College London (UCL)
S. Viti
University College London (UCL)
S. Garcia-Burillo
Spanish National Observatory (OAN)
A. Saintonge
University College London (UCL)
F. Combes
Centre national de la recherche scientifique (CNRS)
A. Fuente
Spanish National Observatory (OAN)
C. Henkel
Max Planck Society
King Abdulaziz University
A. Alonso-Herrero
Spanish National Research Council (CSIC)
N. Harada
Academia Sinica
S. Takano
Nihon University
T. Nakajima
Nagoya University
S. Martin
Atacama Large Millimeter-submillimeter Array (ALMA)
European Southern Observatory Santiago
M. Krips
Institut de Radioastronomie Millimétrique (IRAM)
P. P. van der Werf
Leiden University
Susanne Aalto
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
A. Usero
Spanish National Observatory (OAN)
K. Kohno
University of Tokyo
Monthly Notices of the Royal Astronomical Society
0035-8711 (ISSN) 1365-2966 (eISSN)
Vol. 496 4 5308-5329Subject Categories (SSIF 2011)
Astronomy, Astrophysics and Cosmology
Atom and Molecular Physics and Optics
Other Physics Topics
DOI
10.1093/mnras/staa1891