RSAA Colloquia / Seminars / Feast-of-Facts: Thursday, 30 January 2025, 11:00-12:00; ZOOM or Duffield Lecture Theatre


Anshu Gupta

"MOSEL Survey: Understanding Epoch of Reionisation using galaxies cosmic noon"

In the past two years, the James Webb Space Telescope (JWST) has revolutionized our understanding of the early universe, uncovering galaxies as early as z~14 and revealing that nearly 80–90% of galaxies at z > 6 exhibit extreme emission lines. However, the lack of direct Lyman-continuum detections beyond z > 4.5, combined with limited photometric coverage, challenges our ability to quantify the ionising photon budget of galaxies during the reionisation era. In this talk, I will demonstrate how carefully curated samples of galaxies at cosmic noon (z ~ 2–3) can inform our understanding of early galaxy evolution. My work focuses on extreme emission line galaxies (EELGs) and Lyman-alpha emitters at z ~ 3 to explore the production and escape of ionising radiation, as well as the role of galaxy-galaxy interactions in shaping early galaxies. I will present evidence that mergers trigger recent starbursts in EELGs and promote the escape of Lyman-continuum radiation by inducing asymmetries in the neutral hydrogen gas. I will also show the discovery of a giant (75 kpc) Lyman-alpha nebula at z~3.25 created by interaction of two ~10^10 Msun galaxies that is triggering a new star cluster formation in a dwarf satellite galaxy. These findings shed light on key processes such as gas accretion and Lyman-continuum escape, offering deeper understanding of early galaxy evolution and reionisation.