Pré-Publication, Document De Travail Année : 2021

The Nature of High [OIII]88μm/[CII]158μm Galaxies in the Epoch of Reionization: Low Carbon Abundance and a Top-Heavy IMF?

Harley Katz
Joakim A Rosdahl
Taysun Kimm
Thibault Garel
Joakim A Rosdahl
Martin G. Haehnelt
  • Fonction : Auteur
Léo Michel-Dansac
  • Fonction : Auteur
  • PersonId : 1409263
  • IdRef : 083930523
Sergio Martin-Alvarez
Julien Devriendt
Adrianne Slyz
  • Fonction : Auteur
Romain Teyssier
Pierre Ocvirk
Nicolas Laporte
Richard Ellis
  • Fonction : Auteur

Résumé

ALMA observations of z>6 galaxies have revealed abnormally high [OIII]88μm/[CII]158μm ratios and [CII]158μm deficits compared to local galaxies. Numerous solutions have been proposed including differences in C and O abundance ratios, observational bias, and differences in ISM properties. In order to elucidate the underlying physics that drives this high-redshift phenomenon, we employ SPHINX20, a state-of-the-art, cosmological radiation-hydrodynamics simulation, that resolves detailed ISM properties of thousands of galaxies in the epoch of reionization. We find that the observed z>6 [OIII]-SFR and [CII]-SFR relations can only be reproduced when the C/O abundance ratio is 8× lower than Solar and the total metal production is 4× higher than that of a Kroupa IMF. This implies that high-redshift galaxies are potentially primarily enriched by low-metallicity core-collapse supernovae with a more top-heavy IMF. As AGB stars and type-Ia supernova begin to contribute to the galaxy metallicity, both the [CII]-SFR and [CII] luminosity functions are predicted to converge to observed values at z4.5. While we demonstrate that ionisation parameter, LyC escape fraction, ISM gas density, and CMB attenuation all drive galaxies towards higher [OIII]/[CII], observed values at z>6 can only be reproduced with substantially lower C/O abundances compared to Solar. The combination of [CII] and [OIII] can be used to predict the values of ionisation parameter, ISM gas density, and LyC escape fraction and we provide estimates of these quantities for nine observed z>6 galaxies. Finally, we demonstrate that [OI]63μm can be used as a replacement for [CII] in high-redshift galaxies where [CII] is unobserved and argue that more observation time should be used to target [OI] at z>6. (Abridged)
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Dates et versions

hal-03327419 , version 1 (23-11-2021)

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Harley Katz, Joakim A Rosdahl, Taysun Kimm, Thibault Garel, Joakim A Rosdahl, et al.. The Nature of High [OIII]88μm/[CII]158μm Galaxies in the Epoch of Reionization: Low Carbon Abundance and a Top-Heavy IMF?. 2021. ⟨hal-03327419⟩
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