The distribution and origin of C2H in NGC 253 from ALCHEMI
Artikel i vetenskaplig tidskrift, 2021

Context. Observations of chemical species can provide insights into the physical conditions of the emitting gas however it is important to understand how their abundances and excitation vary within different heating environments. C2H is a molecule typically found in PDR regions of our own Galaxy but there is evidence to suggest it also traces other regions undergoing energetic processing in extragalactic environments. Aims. As part of the ALCHEMI ALMA large program, we map the emission of C2H in the central molecular zone of the nearby starburst galaxy NGC 253 at 1.6″ (28 pc) resolution and characterize it to understand its chemical origins. Methods. We used spectral modeling of the N = 1-0 through N = 4-3 rotational transitions of C2H to derive the C2H column densities towards the dense clouds in NGC 253. We then use chemical modeling, including photodissociation region (PDR), dense cloud, and shock models to investigate the chemical processes and physical conditions that are producing the molecular emission. Results. We find high C2H column densities of ∼1015 cm-2 detected towards the dense regions of NGC 253. We further find that these column densities cannot be reproduced if it is assumed that the emission arises from the PDR regions at the edge of the clouds. Instead, we find that the C2H abundance remains high even in the high visual extinction interior of these clouds and that this is most likely caused by a high cosmic-ray ionization rate.

Astrochemistry

Galaxies: individual: NGC 253

Submillimeter: galaxies

Radiative transfer

Författare

Jonathan Holdship

Universiteit Leiden

University College London (UCL)

Serena Viti

University College London (UCL)

Universiteit Leiden

S. Martin

Atacama Large Millimeter-submillimeter Array (ALMA)

European Southern Observatory Santiago

N. Harada

The Graduate University for Advanced Studies (SOKENDAI)

National Astronomical Observatory of Japan

Academia Sinica

J. G. Mangum

National Radio Astronomy Observatory

K. Sakamoto

Academia Sinica

Sebastien Muller

Chalmers, Rymd-, geo- och miljövetenskap, Onsala rymdobservatorium, Observationssupport

Kunihiko Tanaka

Keio University

Y. Yoshimura

University of Tokyo

K. Nakanishi

The Graduate University for Advanced Studies (SOKENDAI)

National Astronomical Observatory of Japan

R. Herrero-Illana

European Southern Observatory Santiago

Institut de Ciències de l'Espai (ICE) - CSIC

S. Muhle

Universität Bonn

Rebeca Aladro

Max-Planck-Gesellschaft

L. Colzi

Osservatorio Astrofisico di Arcetri

Centro de Astrobiologia (CAB)

K.L. Emig

National Radio Astronomy Observatory

S. G. Burillo

Observatorio Astronómico Nacional (OAN)

C. Henkel

King Abdulaziz University

Max-Planck-Gesellschaft

Pedro Humire

Max-Planck-Gesellschaft

D. S. Meier

New Mexico Institute of Mining and Technology

National Radio Astronomy Observatory Socorro

Víctor M. Rivilla

Centro de Astrobiologia (CAB)

Osservatorio Astrofisico di Arcetri

P. van der Werf

Universiteit Leiden

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 654 A55

Ämneskategorier

Meteorologi och atmosfärforskning

Astronomi, astrofysik och kosmologi

Atom- och molekylfysik och optik

DOI

10.1051/0004-6361/202141233

Mer information

Senast uppdaterat

2021-11-02