Reconstructing the shock history in the CMZ of NGC 253 with ALCHEMI
Journal article, 2023
Context. HNCO and SiO are well-known shock tracers and have been observed in nearby galaxies, including the nearby (D = 3.5 Mpc) starburst galaxy NGC 253. The simultaneous detection of these two species in regions where the star-formation rate is high may be used to study the shock history of the gas. Aims. We perform a multi-line molecular study of NGC 253 using the shock tracers SiO and HNCO and aim to characterize its gas properties. We also explore the possibility of reconstructing the shock history in the central molecular zone (CMZ) of the galaxy. Methods. Six SiO transitions and eleven HNCO transitions were imaged at high resolution 1.ยท6 (28 pc) with the Atacama Large Millimeter/submillimeter Array (ALMA) as part of the ALCHEMI Large Programme. Both non local thermaldynamic equilibrium (non-LTE) radiative transfer analysis and chemical modeling were performed in order to characterize the gas properties and investigate the chemical origin of the emission. Results. The nonLTE radiative transfer analysis coupled with Bayesian inference shows clear evidence that the gas traced by SiO has different densities and temperatures than that traced by HNCO, with an indication that shocks are needed to produce both species. Chemical modeling further confirms such a scenario and suggests that fast and slow shocks are responsible for SiO and HNCO production, respectively, in most GMCs. We are also able to infer the physical characteristics of the shocks traced by SiO and HNCO for each GMC. Conclusions. Radiative transfer and chemical analysis of the SiO and HNCO in the CMZ of NGC 253 reveal a complex picture whereby most of the GMCs are subjected to shocks. We speculate on the possible shock scenarios responsible for the observed emission and provide potential history and timescales for each shock scenario. Observations of higher spatial resolution for these two species are required in order to quantitatively differentiate between the possible scenarios.
Astrochemistry
ISM: molecules
Galaxies: individual: NGC253
Galaxies: starburst
Galaxies: ISM
Author
K. Y. Huang
Leiden University
Serena Viti
University College London (UCL)
Leiden University
Jonathan Holdship
Leiden University
University College London (UCL)
J. G. Mangum
National Radio Astronomy Observatory
S. Martin
Atacama Large Millimeter-submillimeter Array (ALMA)
European Southern Observatory Santiago
N. Harada
National Astronomical Observatory of Japan
Academia Sinica
The Graduate University for Advanced Studies (SOKENDAI)
Sebastien Muller
Chalmers, Space, Earth and Environment, Onsala Space Observatory
K. Sakamoto
Academia Sinica
Kunihiko Tanaka
Keio University
Y. Yoshimura
University of Tokyo
R. Herrero-Illana
Spanish National Research Council (CSIC)
European Southern Observatory Santiago
D. S. Meier
National Radio Astronomy Observatory
New Mexico Institute of Mining and Technology
E. Behrens
University of Virginia
P. van der Werf
Leiden University
C. Henkel
Max Planck Society
King Abdulaziz University
Xinjiang Astronomical Observatory
S. G. Burillo
Spanish National Observatory (OAN)
Víctor M. Rivilla
Centro de Astrobiologia (CAB)
K.L. Emig
National Radio Astronomy Observatory
L. Colzi
Centro de Astrobiologia (CAB)
Pedro Humire
Max Planck Society
Rebeca Aladro
Max Planck Society
M. Bouvier
Leiden University
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 675 A151Subject Categories (SSIF 2011)
Astronomy, Astrophysics and Cosmology
Atom and Molecular Physics and Optics
Geology
DOI
10.1051/0004-6361/202245659