Molecular isotopologue measurements toward super star clusters and the relation to their ages in NGC 253 with ALCHEMI
Artikel i vetenskaplig tidskrift, 2024

Context. Determining the evolution of the CNO isotopes in the interstellar medium (ISM) of starburst galaxies can yield important constraints on the ages of super star clusters (SSCs), or on other aspects and factors contributing to their evolution, such as the initial mass function (IMF). Due to the time-dependent nature of the abundances of isotopes within the ISM -as they are supplied from processes such as nucleosynthesis or chemical fractionation -, this provides the opportunity to test whether or not isotope ratios trace the ages of highly star-forming regions, such as SSCs.
Aims. The goal of this study is to investigate whether the isotopic variations in SSC regions within NGC 253 are correlated with their different ages as derived from stellar population modelling.
Methods. We measured abundance ratios of CO, HCN, and HCO+ isotopologues in six regions containing SSCs within NGC 253 using high-spatial-resolution (1.6″, ~28 pc) data from the ALCHEMI (ALma Comprehensive High-resolution Extragalactic Molecular Inventory) ALMA Large program. We then analysed these ratios using RADEX radiative transfer modelling, with the parameter space sampled using the nested sampling Monte Carlo algorithm MLFriends. These abundance ratios were then compared to ages predicted in each region via the fitting of observed star-formation tracers (such as Brγ) to Starburst99 starburst stellar population evolution models.
Results. We determined the isotopic column density ratios across multiple regions of SSC activity in NGC 253 using non-LTE radiative transfer modelling. We do not find any significant trend with age for the CO and HCN isotopologue ratios on timescales of the ages of the SSC∗ regions observed. However, HCO+ may show a correlation with age over these timescales in 12C/13C.
Conclusions. The driving factors of these ratios within SSCs could be the IMF or fractionation effects. To further probe these effects in SSCs over time, a larger sample of SSCs must be observed spanning a larger age range.

Galaxies: starburst

Galaxies: active

ISM: molecules


Galaxies: ISM


Joshua Butterworth

Universiteit Leiden

Serena Viti

Universiteit Leiden

P. van der Werf

Universiteit Leiden

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)

National Astronomical Observatory of Japan

Academia Sinica

K.L. Emig

National Radio Astronomy Observatory

Sebastien Muller

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

K. Sakamoto

The Graduate University for Advanced Studies (SOKENDAI)

Academia Sinica

Y. Yoshimura

University of Tokyo

Kunihiko Tanaka

Keio University

R. Herrero-Illana

European Southern Observatory Santiago

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

L. Colzi

Centro de Astrobiologia (CAB)

Víctor M. Rivilla

Centro de Astrobiologia (CAB)

K. Y. Huang

Universiteit Leiden

M. Bouvier

Universiteit Leiden

E. Behrens

University of Virginia

C. Henkel


King Abdulaziz University

Xinjiang Astronomical Observatory

Y. T. Yan


D. S. Meier

New Mexico Institute of Mining and Technology

National Radio Astronomy Observatory Socorro

D. Zhou

Danmarks Tekniske Universitet (DTU)

University of British Columbia (UBC)

Cosmic Dawn Center (DAWN)

Universiteit Leiden

Astronomy and Astrophysics

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

Vol. 686 A31


Astronomi, astrofysik och kosmologi

Atom- och molekylfysik och optik

Annan fysik



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