Molecular isotopologue measurements toward super star clusters and the relation to their ages in NGC 253 with ALCHEMI
Journal article, 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.
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
Astrochemistry
ISM: molecules
Galaxies: ISM
Author
Joshua Butterworth
Leiden University
Serena Viti
Leiden University
P. van der Werf
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)
National Astronomical Observatory of Japan
Academia Sinica
K.L. Emig
National Radio Astronomy Observatory
Sebastien Muller
Chalmers, Space, Earth and Environment, Onsala Space Observatory
K. Sakamoto
Academia Sinica
The Graduate University for Advanced Studies (SOKENDAI)
Y. Yoshimura
University of Tokyo
Kunihiko Tanaka
Keio University
R. Herrero-Illana
Spanish National Research Council (CSIC)
European Southern Observatory Santiago
L. Colzi
Centro de Astrobiologia (CAB)
Víctor M. Rivilla
Centro de Astrobiologia (CAB)
K. Y. Huang
Leiden University
M. Bouvier
Leiden University
E. Behrens
University of Virginia
C. Henkel
King Abdulaziz University
Max Planck Society
Xinjiang Astronomical Observatory
Y. T. Yan
Max Planck Society
D. S. Meier
National Radio Astronomy Observatory
New Mexico Institute of Mining and Technology
D. Zhou
Cosmic Dawn Center (DAWN)
Technical University of Denmark (DTU)
Leiden University
University of British Columbia (UBC)
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 686 A31Subject Categories (SSIF 2011)
Astronomy, Astrophysics and Cosmology
Atom and Molecular Physics and Optics
Other Physics Topics
DOI
10.1051/0004-6361/202348787