A giant molecular cloud catalogue in the molecular disc of the elliptical galaxy NGC 5128 (Centaurus A)
Journal article, 2021
We present the first census of giant molecular clouds (GMCs) complete down to 106 M⊙ and within the inner 4 kpc of the nearest giant elliptical and powerful radio galaxy, Centaurus A. We identified 689 GMCs using CO(1-0) data with 1 arcsec spatial resolution (∼20 pc) and 2 km s-1 velocity resolution obtained with the Atacama Large Millimeter/submillimeter Array. The I(CO)-N(H2) conversion factor based on the virial method is XCO = (2 ± 1) × 1020 cm-2(K km s-1)-1 for the entire molecular disc, consistent with that of the discs of spiral galaxies including the Milky Way, and XCO = (5 ± 2) × 1020 cm-2(K km s-1)-1 for the circumnuclear disc (CND; within a galactocentric radius of 200 pc). We obtained the GMC mass spectrum distribution and find that the best truncated power-law fit for the whole molecular disc, with index γ≃ -2.41 ± 0.02 and upper cut-off mass $\sim \! 1.3\times 10^{7}\, \mathrm{M}_{\odot }$, is also in agreement with that of nearby disc galaxies. A trend is found in the mass spectrum index from steep to shallow as we move to inner radii. Although the GMCs are in an elliptical galaxy, the general GMC properties in the molecular disc are as in spiral galaxies. However, in the CND, large offsets in the line-width-size scaling relations (∼0.3 dex higher than those in the GMCs in the molecular disc), a different XCO factor, and the shallowest GMC mass distribution shape (γ= -1.1 ± 0.2) all suggest that there the GMCs are most strongly affected by the presence of the active galactic nucleus and/or shear motions.
Galaxies: individual (NGC 5128)
Galaxies: ISM
ISM: clouds
ISM: molecules
Galaxies: elliptical and lenticular, cD
Author
R.E. Miura
National Astronomical Observatory of Japan
D. Espada
Universidad de Granada
SKA Organisation
A. Hirota
National Astronomical Observatory of Japan
Atacama Large Millimeter-submillimeter Array (ALMA)
C. Henkel
King Abdulaziz University
Max Planck Society
S. Verley
Universidad de Granada
Masato I. N. Kobayashi
Osaka University
Tohoku University
Satoki Matsushita
Academia Sinica
F.P. Israel
Leiden University
B. Vila-Vilaro
European Southern Observatory Santiago
Atacama Large Millimeter-submillimeter Array (ALMA)
K. Morokuma-Matsui
University of Tokyo
JAXA Institute of Space and Astronautical Science
J. Ott
National Radio Astronomy Observatory
C. Vlahakis
National Radio Astronomy Observatory
A. Peck
Gemini Observatory North
Susanne Aalto
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
M. Hogerheijde
University of Amsterdam
Leiden University
N. Neumayer
Max Planck Society
D. Iono
The Graduate University for Advanced Studies (SOKENDAI)
National Astronomical Observatory of Japan
K. Kohno
University of Tokyo
Research Center for the Early Universe
H. Takemura
National Astronomical Observatory of Japan
The Graduate University for Advanced Studies (SOKENDAI)
S. Komugi
Kogakuin University of Technology and Engineering
Monthly Notices of the Royal Astronomical Society
0035-8711 (ISSN) 1365-2966 (eISSN)
Vol. 504 4 6198-6215Subject Categories (SSIF 2011)
Subatomic Physics
Meteorology and Atmospheric Sciences
Astronomy, Astrophysics and Cosmology
DOI
10.1093/mnras/stab1210