Seeing Through the Trough: Outflows and the Detectability of Lyman Alpha Emission from the First Galaxies - Astrophysics > Cosmology and Nongalactic AstrophysicsReport as inadecuate




Seeing Through the Trough: Outflows and the Detectability of Lyman Alpha Emission from the First Galaxies - Astrophysics > Cosmology and Nongalactic Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: The next generation of telescopes aim to directly observe the firstgeneration of galaxies that initiated the reionization process in our Universe.The Lyman Alpha Lya emission line is robustly predicted to be the mostprominent intrinsic spectral feature of these galaxies, making it an idealtarget to search for and study high redshift galaxies. Unfortunately the largeGunn-Peterson optical depth of the surrounding neutral intergalactic mediumIGM is thought to render this line extremely difficult to detect prior toreionization. In this paper we demonstrate that the radiative transfer effectsin the interstellar medium ISM, which cause Lya flux to emerge from galaxiesat frequencies where the Gunn-Peterson optical depth is reduced, cansubstantially enhance the prospects for detection of the Lya line at highredshift. In particular, scattering off outflows of interstellar HI gas canmodify the Lya spectral line shape such that >5% of the emitted Lya radiationis transmitted directly to the observer, even through a fully neutral IGM. Itmay therefore be possible to directly observe `strong- Lya emission lines EW >50 Angstrom rest frame from the highest redshift galaxies that reside in thesmallest HII `bubbles- early in the reionization era with JWST. In addition, weshow that outflows can boost the fraction of Lya radiation that is transmittedthrough the IGM during the latter stages of reionization, and evenpost-reionization. Coupled with the fact that the first generation of galaxiesare thought to have very large intrinsic equivalent Lya equivalent widths, ourresults suggest that the search for galaxies in their redshifted Lya emissionline can be competitive with the drop-out technique out to the highestredshifts that can be probed in the JWST era.



Author: Mark Dijkstra, Stuart Wyithe

Source: https://arxiv.org/







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