Can Galaxy Evolution Mimic Cosmic Reionization?

dc.contributor.authorHassan, S
dc.contributor.authorGronke, M
dc.date.accessioned2022-08-02T19:42:37Z
dc.date.available2022-08-02T19:42:37Z
dc.date.issued2021
dc.description.abstractLyα emitting galaxies are powerful tools to probe the late stages of cosmic reionization. The observed sudden drop in Lyα fraction at z > 6 is often interpreted as a sign of reionization, since the intergalactic medium (IGM) is more neutral and opaque to Lyα photons. Crucially, this interpretation of the observations is only valid under the assumption that galaxies themselves experience a minimal evolution at these epochs. By modeling Lyα radiative transfer effects in and around galaxies, we examine whether a change in the galactic properties can reproduce the observed drop in the Lyα fraction. We find that an increase in the galactic neutral hydrogen content or a reduction in the outflow velocity toward higher redshift both lead to a lower Lyα escape fraction, and can thus mimic an increasing neutral fraction of the IGM. We furthermore find that this change in galactic properties leads to systematically different Lyα spectra which can be used to differentiate the two competing effects. Using the CANDELSz7 survey measurements which indicate slightly broader lines at z ∼ 6, we find that the scenario of a mere increase in the galactic column density toward higher z is highly unlikely. We also show that a decrease in outflow velocity is not ruled out by existing data but leads to more prominent blue peaks at z > 6. Our results caution using Lyα observations to estimate the IGM neutral fraction without accounting for the potential change in the galactic properties, e.g., by mapping out the evolution of Lyα spectral characteristics.en_US
dc.identifier.citationHassan, Sultan, and Max Gronke. “Can Galaxy Evolution Mimic Cosmic Reionization?” arXiv.org (2021): n. pag. Web.en_US
dc.identifier.issn1538-4357
dc.identifier.issn0004-637X
dc.identifier.urihttp://iopscience.iop.org/0004-637X
dc.identifier.urihttp://hdl.handle.net/10566/7658
dc.language.isoenen_US
dc.publisherIOP Publishingen_US
dc.subjectastrophysicalen_US
dc.subjectgalaxy evolutionen_US
dc.subjectcosmic reionizationen_US
dc.subjectastronomyen_US
dc.titleCan Galaxy Evolution Mimic Cosmic Reionization?en_US
dc.typeArticleen_US

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