Kavli Affiliate: Roberto Maiolino
| Summary:
The properties of the first metal-free stars remain largely unknown, and so far, the only data-driven constraints on their mass distribution (IMF) come from near-field cosmology. Here, we interpret new observations of the C1 and C2 components of Hebe, the HeII emitter near the galaxy GN-z11. Using a locally calibrated model, we robustly confirm the pristine (PopIII) nature of both components, showing that the measured upper limits on metal lines can only be reproduced by galaxies with $>50%$ of their stellar mass in PopIII stars. We find that C1 is consistent with a purely PopIII system and adopt a simple parametric approach to infer the implications for the PopIII IMF and stellar mass. The observed $rm HeII/H_γ$ ratio excludes steep IMFs, favoring top-heavy distributions, especially for young stellar ages ($leq 1$ Myr). Combined with the HeII luminosity, this implies a total PopIII stellar mass of $2 cdot 10^4 < M_star/M_odot < 6 cdot 10^5$. While degeneracies between IMF, stellar mass, and age remain, adopting the lower stellar masses predicted by simulations ($M_star < 10^5,M_odot$) strengthens the preference for top-heavy IMFs. Combining these results with near-field constraints, which instead exclude the flattest IMFs, we define a data-driven range of viable PopIII IMFs, linking characteristic mass and slope. This work demonstrates that direct observations of high-$z$ PopIII systems can place independent constraints on the IMF of the first stars, opening a new window on their formation and properties.
| Search Query: arXiv Query: search_query=au:”Maiolino Roberto”&id_list=&start=0&max_results=10
Read More