Institute of Astronomy

JWST reveals galaxy mergers driving Lyman-alpha emission at z >7

SpeakerTalk DateTalk Series
Callum Witten15 February 2023Institute of Astronomy Seminars


One of the key, unsolved questions in modern-day astronomy regards the sources of the ionizing photons that drove reionization. Recent debates focus on whether a hard radiation field emanating from a single galaxy, or an enhanced radiation field provided by an overdensity of associated objects can produce the required ionizing photons to create the ionized bubbles that are observed at z >7. Observations of Lyman-alpha emitters (LAEs) resident in significant overdensities (protoclusters) have been complicated by the detection of AGN candidates additionally present within many of these bubbles. However, we present results from JWST/NIRCam imaging that reveal, for the first time, resolved z >7 observations of LAEs, giving new insights into their intrinsic properties. These new observations indicate all three known LAEs at z >7, that have been observed by NIRCam, are undergoing mergers that were previously unresolved by HST. Combining these results with simulations of interacting systems we postulate a third solution to this unsolved mystery – Lya emission driven by interactions with a companion.


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