Methanol masers in NGC 253 with ALCHEMI
Artikel i vetenskaplig tidskrift, 2022
Context. Methanol masers of Class I (collisionally pumped) and Class II (radiatively pumped) have been studied in great detail in our Galaxy in a variety of astrophysical environments such as shocks and star-forming regions and are they are helpful to analyze the properties of the dense interstellar medium. However, the study of methanol masers in external galaxies is still in its infancy.
Aims. Our main goal is to search for methanol masers in the central molecular zone (CMZ; inner 500 pc) of the nearby starburst galaxy NGC253. Methods. Covering a frequency range between 84 and 373 GHz (λ = 3.6-0.8 mm) at high angular (1."6 ∼ 27 pc) and spectral (∼8-9 km s-1) resolution with ALCHEMI (ALMA Comprehensive High-resolution Extragalactic Molecular Inventory), we have probed dierent regions across the CMZ of NGC253. In order to look for methanol maser candidates, we employed the rotation diagram method and a set of radiative transfer models. Results.We detect for the first time masers above 84 GHz in NGC253, covering an ample portion of the J-1 (J-1)0-E line series (at 84, 132, 229, and 278 GHz) and the J0 (J-1)1 A series (at 95, 146, and 198 GHz). This confirms the presence of the Class I maser line at 84 GHz, which was already reported, but now being detected in more than one location. For the J-1 (J-1)0-E line series, we observe a lack of Class I maser candidates in the central star-forming disk.
Conclusions. The physical conditions for maser excitation in the J-1 (J-1)0-E line series can be weak shocks and cloud-cloud collisions as suggested by shock tracers (SiO and HNCO) in bi-symmetric shock regions located in the outskirts of the CMZ. On the other hand, the presence of photodissociation regions due to a high star-formation rate would be needed to explain the lack of Class I masers in the very central regions.
Aims. Our main goal is to search for methanol masers in the central molecular zone (CMZ; inner 500 pc) of the nearby starburst galaxy NGC253. Methods. Covering a frequency range between 84 and 373 GHz (λ = 3.6-0.8 mm) at high angular (1."6 ∼ 27 pc) and spectral (∼8-9 km s-1) resolution with ALCHEMI (ALMA Comprehensive High-resolution Extragalactic Molecular Inventory), we have probed dierent regions across the CMZ of NGC253. In order to look for methanol maser candidates, we employed the rotation diagram method and a set of radiative transfer models. Results.We detect for the first time masers above 84 GHz in NGC253, covering an ample portion of the J-1 (J-1)0-E line series (at 84, 132, 229, and 278 GHz) and the J0 (J-1)1 A series (at 95, 146, and 198 GHz). This confirms the presence of the Class I maser line at 84 GHz, which was already reported, but now being detected in more than one location. For the J-1 (J-1)0-E line series, we observe a lack of Class I maser candidates in the central star-forming disk.
Conclusions. The physical conditions for maser excitation in the J-1 (J-1)0-E line series can be weak shocks and cloud-cloud collisions as suggested by shock tracers (SiO and HNCO) in bi-symmetric shock regions located in the outskirts of the CMZ. On the other hand, the presence of photodissociation regions due to a high star-formation rate would be needed to explain the lack of Class I masers in the very central regions.
Masers
Submillimeter: Galaxies
Radio lines: Galaxies
Galaxies: Starburst
Galaxies: Spiral
Författare
Pedro Humire
Max-Planck-Gesellschaft
C. Henkel
King Abdulaziz University
Max-Planck-Gesellschaft
Chinese Academy of Sciences
A. Hernández-Gómez
Max-Planck-Gesellschaft
S. Martin
Atacama Large Millimeter-submillimeter Array (ALMA)
European Southern Observatory Santiago
J. G. Mangum
National Radio Astronomy Observatory
N. Harada
National Astronomical Observatory of Japan
The Graduate University for Advanced Studies (SOKENDAI)
Academia Sinica
Sebastien Muller
Chalmers, Rymd-, geo- och miljövetenskap, Onsala rymdobservatorium
K. Sakamoto
Academia Sinica
Kunihiko Tanaka
Keio University
Y. Yoshimura
University of Tokyo
Kouichiro Nakanishi
National Astronomical Observatory of Japan
The Graduate University for Advanced Studies (SOKENDAI)
S. Muhle
Universität Bonn
R. Herrero-Illana
European Southern Observatory Santiago
Consejo Superior de Investigaciones Científicas (CSIC)
D. S. Meier
New Mexico Institute of Mining and Technology
National Radio Astronomy Observatory Socorro
E. Caux
Universite Paul Sabatier Toulouse III
Rebeca Aladro
Max-Planck-Gesellschaft
R. Mauersberger
Max-Planck-Gesellschaft
Serena Viti
Universiteit Leiden
University College London (UCL)
L. Colzi
Centro de Astrobiologia (CAB)
Víctor M. Rivilla
Centro de Astrobiologia (CAB)
Mark Gorski
Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik
K. Menten
Max-Planck-Gesellschaft
K. Y. Huang
Universiteit Leiden
Susanne Aalto
Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik
P. van der Werf
Universiteit Leiden
K.L. Emig
National Radio Astronomy Observatory
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 663 A33Ämneskategorier (SSIF 2011)
Meteorologi och atmosfärforskning
Astronomi, astrofysik och kosmologi
Atom- och molekylfysik och optik
DOI
10.1051/0004-6361/202243384