Modeling Stellar Population Spectra: Exploring Parameter Space for The Largest Balmer Break*

JWST's recent discovery of luminous, compact, red objects in the high-redshift universe nicknamed Little Red Dots (LRDs) exhibit unusually large balmer break strengths. This project uses the same method of measuring balmer break strengths as in De Graaff et al. 2025, where the LRD RUBIES-UDS-15418 is found to have a break strength of 6.9. These peculiar LRD sources pose the question whether there could exist an ordinary stellar population capable of reproducing similarly impressive balmer break strengths. This project first performs a comprehensive sampling of spectra in Prospector of parameters such as age, metallicity, and dust attenuation.  It was found that any dust attenuation on the models would increase the break strength monotonically, so in final samplings, the dust attenuation parameter was set to 0. After creating a finely meshed grid of 60,000 models, the maximum break strength of 2.926 was found to occur at dust=0, log(Z☉)=0.5 and age=356.4 Myrs. The project continues its search by executing a Markov Chain Monte Carlo (MCMC) sampling of Star Formation History (SFH) parameters using Python’s emcee. In this search, dust, log(metallicity) and age are set to 0.0, 0.5 Z☉ and 350 Myrs respectively. The MCMC search results in a best-fit model with a measured break strength of 2.7573, however, the probability distributions for parameters tau, const, and fburst suggest these might be degenerate.