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The evolution of CNO isotopes: a new window on cosmic star formation history and the stellar IMF in the age of ALMA

Romano, D., Matteucci, F., Zhang, Z.-Y., Papadopoulos, Pantelis and Ivison, R. J. 2017. The evolution of CNO isotopes: a new window on cosmic star formation history and the stellar IMF in the age of ALMA. Monthly Notices of the Royal Astronomical Society 470 (1) , pp. 401-415. 10.1093/mnras/stx1197

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Abstract

We use state-of-the-art chemical models to track the cosmic evolution of the CNO isotopes in the interstellar medium of galaxies, yielding powerful constraints on their stellar initial mass function (IMF). We re-assess the relative roles of massive stars, asymptotic giant branch (AGB) stars and novae in the production of rare isotopes such as 13C, 15N, 17O and 18O, along with 12C, 14N and 16O. The CNO isotope yields of super-AGB stars, novae and fast-rotating massive stars are included. Having reproduced the available isotope enrichment data in the solar neighbourhood, and across the Galaxy, and having assessed the sensitivity of our models to the remaining uncertainties, e.g. nova yields and star formation history, we show that we can meaningfully constrain the stellar IMF in galaxies using C, O and N isotope abundance ratios. In starburst galaxies, where data for multiple isotopologue lines are available, we find compelling new evidence for a top-heavy stellar IMF, with profound implications for their star formation rates and efficiencies, perhaps also their stellar masses. Neither chemical fractionation nor selective photodissociation can significantly perturb globally averaged isotopologue abundance ratios away from the corresponding isotope ones, as both these processes will typically affect only small mass fractions of molecular clouds in galaxies. Thus, the Atacama Large Millimeter Array now stands ready to probe the stellar IMF, and even the ages of specific starburst events in star-forming galaxies across cosmic time unaffected by the dust obscuration effects that plague optical/near-infrared studies.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Publisher: Oxford University Press
ISSN: 0035-8711
Funders: STFC
Date of First Compliant Deposit: 13 July 2017
Date of Acceptance: 12 May 2017
Last Modified: 14 Jul 2017 09:29
URI: http://orca-mwe.cf.ac.uk/id/eprint/102372

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