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.

Galaxies: starburst

Astrochemistry

ISM: molecules

Galaxies: ISM

Galaxies: individual: NGC253

Author

K. Y. Huang

Leiden University

Serena Viti

University College London (UCL)

Leiden University

Jonathan Holdship

University College London (UCL)

Leiden University

J. G. Mangum

National Radio Astronomy Observatory

S. Martin

European Southern Observatory Santiago

Atacama Large Millimeter-submillimeter Array (ALMA)

N. Harada

The Graduate University for Advanced Studies (SOKENDAI)

Academia Sinica

National Astronomical Observatory of Japan

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

Institute of Space Sciences (ICE) - CSIC

European Southern Observatory Santiago

D. S. Meier

National Radio Astronomy Observatory Socorro

New Mexico Institute of Mining and Technology

E. Behrens

University of Virginia

P. van der Werf

Leiden University

C. Henkel

Xinjiang Astronomical Observatory

Max Planck Society

King Abdulaziz University

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 A151

Subject Categories

Astronomy, Astrophysics and Cosmology

Atom and Molecular Physics and Optics

Geology

DOI

10.1051/0004-6361/202245659

More information

Latest update

8/11/2023