Seeking Edge-on Galaxies with Substantial Extraplanar Dust Using a Radiative Transfer Model: Determination of the Model Parameter Uncertainties for EON_10.477_41.954 (FGC 79)

TL;DR

This study uses Markov-Chain Monte Carlo analysis to accurately estimate uncertainties in a radiative transfer galaxy model, revealing larger confidence intervals than previous estimates, and confirming the galaxy's classification with substantial extraplanar dust.

Contribution

It introduces a rigorous MCMC approach to quantify model parameter uncertainties in galaxy classification, emphasizing the importance of convergence diagnostics.

Findings

Effective sample sizes exceeded 5,650 for all parameters.

Final confidence intervals are 5-100 times larger than previous nominal uncertainties.

Galaxy EON_10.477_41.954 remains classified as having substantial extraplanar dust.

Abstract

We have revisited the target EON_10.477_41.954 in order to determine more accurately the uncertainties in the model parameters that are important for target classification (i.e., galaxies with or without substantial extraplanar dust). We performed a Markov-Chain Monte Carlo (MCMC) analysis for the fifteen parameters of the three-dimensional radiative-transfer galaxy model we used previously for target classification. To investigate the convergence of the MCMC sampling---which is usually neglected in the literature but should not be---we monitored the integrated autocorrelation time ($\tau_{int}$), and we achieved effective sample sizes $>5,650$ for all the model parameters. The confidence intervals are unstable at the beginning of the iterations where the values of $\tau_{int}$ are increasing, but they become stable in later iterations where those values are almost constant. The final confidence intervals are $\sim5-100$ times larger than the nominal uncertainties used in our previous study (the standard deviation of three best-fit results). Thus, those nominal uncertainties are not good proxies for the model-parameter uncertainties. Although the position of EON_10.477_41.954 in the target-classification plot (the scale-height to diameter ratio of dust vs that of light-source) decreases by about $20-30$ % when compared to our previous study, its membership in the ``high-group''---i.e., among galaxies with substantial extraplanar dust---nevertheless remains unchanged.