Predicting Lyman-continuum emission of galaxies using their physical and Lyman-alpha emission properties

Moupiya Maji, Anne Verhamme, Joakim Rosdahl, Thibault Garel, Jérémy Blaizot, Valentin Mauerhofer, Marta Pittavino, Maria Pia Victoria Feser, Mathieu Chuniaud, Taysun Kimm, Harley Katz, Martin Haehnelt

Research output: Contribution to journalArticlepeer-review

Abstract

Aims. The primary difficulty in understanding the sources and processes that powered cosmic reionization is that it is not possible to directly probe the ionizing Lyman-continuum (LyC) radiation at that epoch as those photons have been absorbed by the intervening neutral hydrogen. It is therefore imperative to build a model to accurately predict LyC emission using other properties of galaxies in the reionization era. Methods. In recent years, studies have shown that the LyC emission from galaxies may be correlated to their Lyman-alpha (Lyα) emission. In this paper we study this correlation by analyzing thousands of simulated galaxies at high redshift in the SPHINX cosmological simulation. We post-process these galaxies with the Lyα radiative transfer code RASCAS and analyze the Lyα - LyC connection. Results. We find that the Lyα and LyC luminosities are strongly correlated with each other, although with dispersion. There is a positive correlation between the escape fractions of Lyα and LyC radiations in the brightest Lyman-alpha emitters (LAEs; escaping Lyα luminosity LescLyα > 1041 erg s-1), similar to that reported by recent observational studies. However, when we also include fainter LAEs, the correlation disappears, which suggests that the observed relation may be driven by selection effects. We also find that the brighter LAEs are dominant contributors to reionization, with LescLyα > 1040 erg s-1 galaxies accounting for > 90% of the total amount of LyC radiation escaping into the intergalactic medium in the simulation. Finally, we build predictive models using multivariate linear regression, where we use the physical and Lyα properties of simulated reionization era galaxies to predict their LyC emission. We build a set of models using different sets of galaxy properties as input parameters and predict their intrinsic and escaping LyC luminosity with a high degree of accuracy (the adjusted R2 of these predictions in our fiducial model are 0.89 and 0.85, respectively, where R2 is a measure of how much of the response variance is explained by the model). We find that the most important galaxy properties for predicting the escaping LyC luminosity of a galaxy are its LescLyα, gas mass, gas metallicity, and star formation rate. Conclusions. These results and the predictive models can be useful for predicting the LyC emission from galaxies using their physical and Lyα properties and can thus help us identify the sources of reionization.

Original languageEnglish
Article numberA66
JournalAstronomy and Astrophysics
Volume663
DOIs
Publication statusPublished - 2022 Jul 1

Bibliographical note

Funding Information:
We thank the anonymous referee for valuable comments and suggestions that have substantially improved the paper. MM, AV and TG are supported by the ERC Starting grant 757258 'TRIPLE'. AV acknowledges support from SNF Professorship PP00P2-176808. TK was supported by the National Research Foundation of Korea (NRF-2019K2A9A1A0609137711 and NRF-2020R1C1C1007079). We have performed the radiative transfer calculations in the LESTA and BAOBAB high-performance computing clusters of University of Geneva, and the RT post-processing for 1933 halos took approximately -37 000 CPU hours. The SPHINX simulation results of this research have been achieved using the PRACE Research Infrastructure resource Super- MUC based in Garching, Germany, under PRACE grant 2016153539. We additionally acknowledge support and computational resources from the Common Computing Facility (CCF) of the LABEX Lyon Institute of Origins (ANR-10- LABX-66).

Funding Information:
Acknowledgements. We thank the anonymous referee for valuable comments and suggestions that have substantially improved the paper. MM, AV and TG are supported by the ERC Starting grant 757258 ‘TRIPLE’. AV acknowledges support from SNF Professorship PP00P2_176808. TK was supported by the National Research Foundation of Korea (NRF-2019K2A9A1A0609137711 and NRF-2020R1C1C1007079). We have performed the radiative transfer calculations in the LESTA and BAOBAB high-performance computing clusters of University of Geneva, and the RT post-processing for 1933 halos took approximately ∼37 000 CPU hours. The SPHINX simulation results of this research have been achieved using the PRACE Research Infrastructure resource Super-MUC based in Garching, Germany, under PRACE grant 2016153539. We additionally acknowledge support and computational resources from the Common Computing Facility (CCF) of the LABEX Lyon Institute of Origins (ANR-10-LABX-66).

Publisher Copyright:
© ESO 2022.

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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