2023/03/21 by Mitchell T Dennis, Jeremy Sakstein, Dennis, Mitchell +1
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics of Galaxies (astro-ph.GA) #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #Solar and Stellar Astrophysics (astro-ph.SR) #Stellar, planetary, and galactic studies
paper · pdf · doi:10.48550/arxiv.2303.12069
openalex publication_date 2023/03/21 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
A method for investigating the sensitivity of the tip of the red giant branch (TRGB) I band magnitude MI to stellar input physics is presented.~We compute a grid of ∼125,000 theoretical stellar models with varying mass, initial helium abundance, and initial metallicity, and train a machine learning emulator to predict MI as a function of these parameters.~First, our emulator can be used to theoretically predict MI in a given galaxy using Monte Carlo sampling.~As an example, we predict MI = -3.87+0.11-0.08 in the Large Magellanic Cloud (F20).~Second, our emulator enables a direct comparison of theoretical predictions for MI with empirical calibrations to constrain stellar modeling parameters using Bayesian Markov Chain Monte Carlo methods.~We demonstrate this by using empirical TRGB calibrations to obtain new independent measurements of the metallicity in three galaxies.~We find log10(Z)=-2.167+0.404-0.492 and log10(Z)=-2.098+0.388-0.528 in the Large Magellanic Cloud (F20 and Y19 respectively), log10(Z)=-2.146+0.400-0.505 in NGC 4258, and log10(Z)=-2.143+0.401-0.508 in ω-Centauri.~The LMC and NGC 4258 measurements are consistent with other measurements within <1σ errors, and the ω-Centauri measurement are within <2σ errors.