CTC Seminar: Alessandra Venditti (UT Austin), The surprising lives of Pop III stars: whens, wheres and hows

The surprising lives of Pop III stars: whens, wheres and hows

Alessandra Venditti 
Cosmic Frontier Center Prize Research Fellow

Abstract: The search and characterization of the first, Population III (Pop III) stars is a central goal of modern astrophysics. These stars are predicted to start forming at Cosmic Dawn (z~20−30) from molecular-cooling mini-halos (~10⁵−10⁶ M⊙), and to be predominantly massive, shaping early galaxy evolution, cosmic metal enrichment and reionization. However, theory also allows efficient Pop III star formation in pristine clouds within high-mass, atomic-cooling halos (≳10⁸ M⊙), potentially persisting well into the Epoch of Reionization (EoR, z~6−10) and coexisting with second-generation (Pop II) stars. 

JWST has opened concrete prospects for detecting such systems. Tentative constraints on the Pop III ultra-violet luminosity function (UVLF) at z≃5.6−6.6 hint at an unexpectedly UV-bright Pop III population, and candidate Pop III systems have been reported at z~3−10 using joint low-metallicity and spectral-hardness diagnostics. Yet no Pop III-dominated galaxy has been confirmed, motivating the need for broader searches and robust confirmation strategies. In this talk, I will discuss interpretations of these exciting findings, and outline avenues for identifying Pop III stars in and around massive EoR galaxies via HeII rest-UV and optical lines, while also quantifying confusion from nearby young Pop II populations.

Host: Ankita Bera