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Indirect probes of Lyman continuum escape from galaxies

Applicant Verhamme Anne
Number 176808
Funding scheme SNSF Professorships
Research institution Observatoire de Genève Université de Genève
Institution of higher education University of Geneva - GE
Main discipline Astronomy, Astrophysics and Space Sciences
Start/End 01.10.2018 - 30.09.2022
Approved amount 1'445'790.00
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Keywords (6)

cosmic reionisation; galaxy formation; radiation transfer; galaxy evolution; radiation hydrodynamics simulations; resonant transition

Lay Summary (French)

Au cours du premier milliard d'années de l'Univers, l'apparition des sources lumineuses réchauffe la matière. L'existence de cette transition de phase primordiale, appelée Réionisation cosmique, est bien établie, mais la nature des sources de la réionisation est toujours débattue aujourd'hui.
Lay summary
L'objectif principal de ce project de recherche est de contribuer à découvrir la nature des sources de la réionisation cosmique, en utilisant à la fois simulations numériques et observations, pour tester plusieurs diagnostics indirects d'échappement des photons ionisants des galaxies. 
Direct link to Lay Summary Last update: 02.10.2018

Responsible applicant and co-applicants


Associated projects

Number Title Start Funding scheme
158378 Spectral diagnostics to study the escape of ionizing photons and gas flows around galaxies 01.09.2015 Marie Heim-Voegtlin grants


Cosmic reionization corresponds to the period in the history of the Universe during which the predominantly neutral intergalactic medium was ionized by the emergence of the first luminous sources. Young stars in primeval galaxies may be the sources of reionization, if the ionizing radiation, called Lyman continuum (LyC), that they produce can escape their interstellar medium: the escape fraction of LyC photons from galaxies is one of the main unknowns of reionization studies. This project will contribute to make progess on this issue, by testing indirect diagnostics of LyC leakage that were recently reported in the literature, and comparing the observations with the direct escape of LyC photons from galaxies, and with simulations. The first diagnostic for LyC leakage relates the escape of the strongly resonant Lyman-alpha radiation from galaxies to the LyC escape. It was proposed by the applicant (Verhamme et al. 2015), and recently validated by first observations (Verhamme et al. 2017). The second diagnostic proposes that the strength of Oxygen lines ratios can trace density-bounded interstellar regions. It was the selection criterion for the successful detection of 5 strong Lyman Continuum Emitters from our team (Izotov et al. 2016a, 2016b). A third diagnostic relates the metallic absorption line strengths to the porosity of the absorbing interstellar gas in front of the stars. The increasing opacity of the intergalactic medium with redshift renders direct LyC detection impossible during reionization. Indirect methods are the only probes of LyC leakage in the distant Universe, and the proposed diagnostics will soon become observable at the redshifts of interest with JWST. They have passed the validation tests on a pilot study of five objects, we propose now to calibrate the escape of LyC emission from galaxies on large datasets in a systematic way. These are the main objectives of this project.Complemented by european funding, the proposed project will allow me to start my own research group, in a vibrant domain of astrophysics with a lot of upcoming developments and perspectives, and will ideally place me to establish my research group in Geneva or other places in the near future.