Determine the mass of any older underlying stellar population

Determine whether U13151 contains an older underlying stellar population and measure its stellar mass using observations that constrain the rest-frame optical continuum.

Background

The observed emission from U13151 is dominated by a very young stellar component, but the non-detection in MIRI/F1000W prevents a robust constraint on the rest-frame optical continuum. As a result, the contribution of an older population is poorly determined and only an upper limit can be reported.

Establishing whether such a population exists is important for deciding whether most of the galaxy’s stellar mass was assembled in the current burst or in earlier episodes.

References

Although our SED modeling also allows for an underlying older stellar population, its contribution remains largely unconstrained by the available data. In particular, the non-detection of U13151 in MIRI/F1000W limits our ability to constrain the rest-frame optical continuum and, consequently, to establish the presence and stellar mass of a potentially older population.

— PRISMS/U13151. A Glimpse into the Earliest Phases of Galaxy Formation through an Ultra-Faint System $\approx$ 500 Myr after the Big Bang  (2610.26560 - Rinaldi et al., 19 Oct 2026) in Section 3.1.2, “Insights from photometry and SED fitting”; summarized in Section 5