Measuring Resolved Star Formation Histories from High-Precision Color-Magnitude Diagrams with StarFormationHistories.jl

TL;DR

This paper introduces StarFormationHistories.jl, an open-source Julia package designed to measure detailed star formation histories from high-precision color-magnitude diagrams, accommodating various population parameters and uncertainties.

Contribution

The paper presents a flexible, modular Julia tool for deriving resolved star formation histories, including modeling of binaries, arbitrary IMFs, and uncertainty quantification, with application to JWST and HST data.

Findings

Successfully applied to JWST/NIRCAM data of WLM galaxy

Analyzed HST/ACS data of Horologium I dwarf galaxy

Demonstrated flexibility in modeling population parameters

Abstract

Understanding how and when galaxies formed stars over the history of the Universe is fundamental to the study of galaxy evolution. The star formation histories (SFHs) of galaxies in the local Universe can be measured with high precision using deep imaging with space telescopes. Such \emph{resolved} SFHs are based on modelling the observed color-magnitude diagram (CMD) with stellar evolution models and rely on age-sensitive features like the main sequence turn-off to measure a galaxy's star formation rate as a function of time. There are many other population-level parameters that factor into these measurements, such as the stellar initial mass function (IMF), binary fraction, and metallicity, to name a few. We present and release StarFormationHistories$.$jl, a modular, open-source Julia package for measuring resolved SFHs with a focus on model flexibility for these types of population parameters. The code can model unresolved photometric binaries and supports arbitrary IMFs. Random uncertainties in the SFH measurements can be quantified with Monte Carlo posterior sampling methods. We illustrate the performance of the package on JWST/NIRCAM data of the Local Group dwarf irregular galaxy WLM $\left(M_v\approx-14.2 \ \text{mag}\right)$, which exhibits a complex, well-sampled CMD, and HST/ACS data of the ultra-faint Milky Way satellite dwarf galaxy Horologium I $\left(M_v\approx-3.7 \ \text{mag}\right)$, which has a much simpler but sparser CMD.