Around 400 million years after the Big Bang, the ultraviolet emission from star-forming galaxies reionized the Universe. Ionizing radiation (Lyman Continuum, LyC) is absorbed by cold neutral hydrogen gas (HI) within galaxies, hindering the escape of LyC photons. Since the HI reservoir of LyC emitters has never been mapped, major uncertainties remain on how LyC photons escape galaxies and ionize the intergalactic medium. We have directly imaged the neutral gas in the nearby reionization-era analog galaxy Haro 11 with the 21cm line to identify the mechanism enabling ionizing radiation escape. We find that merger-driven interactions have caused a bulk offset of the neutral gas by about 6 kpc from the center of the galaxy, where LyC emission production sites are located. This could facilitate the escape of ionizing radiation into our line of sight. Galaxy interactions can cause both elevated LyC production and large-scale displacement of HI from the regions where these photons are produced. They could contribute to the anisotropic escape of LyC radiation from galaxies and the reionization of the Universe. We argue for a systematic assessment of the effect of environment on LyC production and escape.
@article{arxiv.2301.02676,
title = {Tidally offset neutral gas in Lyman continuum emitting galaxy Haro 11},
author = {Alexandra Le Reste and John M. Cannon and Matthew J. Hayes and John L. Inoue and Amanda A. Kepley and Jens Melinder and Veronica Menacho and Angela Adamo and Arjan Bik and Timmy Ejdetjärn and Gyula I. G. Józsa and Göran Östlin and Sarah H. Taft},
journal= {arXiv preprint arXiv:2301.02676},
year = {2023}
}
Comments
15 pages, 9 figures, accepted for publication in MNRAS