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The First Stars and Galaxies: Challenges for the Next Decade Participants
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Talk
Title: The Lyman-Alpha Signatures of the First Galaxies Author(s): Mark Dijkstra Abstract: The next generation of telescopes aim to directly observe the first generation of galaxies that initiated the reionization process in our Universe. The Lyman Alpha (Lya) emission line is robustly predicted to be the most prominent intrinsic spectral feature of these galaxies. The large Gunn-Peterson optical depth of the surrounding neutral intergalactic medium (IGM) is thought to render this line extremely difficult to detect. However, radiative transfer effects in the interstellar medium (ISM) of galaxies can cause Lya flux to emerge from galaxies at frequencies where the Gunn-Peterson optical depth is reduced significantly. In particular, scattering off outflows of interstellar HI gas can modify the Lya spectral line shape such that > 5% of the emitted Lya radiation is transmitted directly to the observer, even through a fully neutral IGM. It may therefore well be possible to directly observe `strong' Lya emission lines (EW>50 Angstrom rest frame) from the highest redshift galaxies with e.g. JWST.
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