HOLy GraLeS: High resolution Observations of Lyman emission in Gravitationally Lensed Starbursts

In the Epoch of Reionization between 100 million and one billion years after Big Bang, strong Lyman-Continuum (LyC) radiation from the first galaxies ionized the previously neutral intergalactic medium. How this LyC radiation escaped is not well known. Star forming galaxies are rich with neutral hydrogen which absorbs LyC.

Something must have created passageways through this gas, allowing a large fraction of the LyC photons to escape into intergalactic Space. However, in the local Universe, at present time, only a tiny fraction of LyC photons escape their galaxies. The escape must depend on factors that have evolved over time.

To solve this, it is necessary to study the production and escape of LyC photons in greates possible detail.

This is however difficult: in the nearby Universe, technical limitations of the Hubble telescope mean that LyC can only be localized with an accuracy of ~ 1 kpc; and at redshifts sufficiently high to overcome these limitations, the distance is too large to allow any detailed study. In 2019, I published the discovery that the gravitationally lensed Sunburst Arc at z=2.4 was emitting strong LyC.

The galaxy is so highly magnified that it shows detail  comparable to some in the nearby Universe. This project builds on an approved program to observe it with JWST. This allows an unprecedentedly detailed study of the passage of LyC through its interstellar medium. In addition, I will systematically search for more such LyC leaking, lensed galaxies.