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13C/18O ratio as a litmus test of stellar IMF variations in high-redshift starbursts

Published online by Cambridge University Press:  04 June 2020

Donatella Romano Open the ORCID record for Donatella Romano [Opens in a new window] ,
Zhi-Yu Zhang ,
Francesca Matteucci ,
Rob J. Ivison  and
Padelis P. Papadopoulos
Donatella Romano
Affiliation:
INAF, Astrophysics and Space Science Observatory, Via Gobetti 93/3, I-40129 Bologna, Italy email: donatella.romano@inaf.it
Zhi-Yu Zhang
Affiliation:
Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ, UK European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748, Garching bei München, Germany
Francesca Matteucci
Affiliation:
Physics Department, Section of Astronomy, University of Trieste, Via Tiepolo 11, I-34131, Trieste, Italy INAF, Astronomical Observatory of Trieste, Via Tiepolo 11, I-34131, Trieste, Italy
Rob J. Ivison
Affiliation:
Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ, UK European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748, Garching bei München, Germany
Padelis P. Papadopoulos
Affiliation:
Physics Department, Section of Astrophysics, Astronomy and Mechanics, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
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Abstract

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Determining the shape of the stellar initial mass function (IMF) and whether it is constant or varies in space and time is the Holy Grail of modern astrophysics, with profound implications for all theories of star and galaxy formation. On a theoretical ground, the extreme conditions for star formation (SF) encountered in the most powerful starbursts in the Universe are expected to favour the formation of massive stars. Direct methods of IMF determination, however, cannot probe such systems, because of the severe dust obscuration affecting their starlight. The next best option is to observe CNO bearing molecules in the interstellar medium at millimetre/ submillimetre wavelengths, which, in principle, provides the best indirect evidence for IMF variations. In this contribution, we present our recent findings on this issue. First, we reassess the roles of different types of stars in the production of CNO isotopes. Then, we calibrate a proprietary chemical evolution code using Milky Way data from the literature, and extend it to discuss extragalactic data. We show that, though significant uncertainties still hamper our knowledge of the evolution of CNO isotopes in galaxies, compelling evidence for an IMF skewed towards high-mass stars can be found for galaxy-wide starbursts. In particular, we analyse a sample of submillimetre galaxies observed by us with the Atacama Large Millimetre Array at the peak of the SF activity of the Universe, for which we measure 13C/18O⋍1. This isotope ratio is especially sensitive to IMF variations, and is little affected by observational uncertainties. At the end, ongoing developments of our work are briefly outlined.

Keywords

nuclear reactionsnucleosynthesisabundancesgalaxies: abundancesgalaxies: evolutiongalaxies: ISMgalaxies: starburststars: luminosity functionmass function
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 15 , Symposium S352: Uncovering Early Galaxy Evolution in the ALMA and JWST Era , June 2019 , pp. 234 - 238
Copyright
© International Astronomical Union 2020

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