Sizing Up the Milky Way: A Bayesian Mixture Model Meta-Analysis of Photometric Scale Length Measurements

Understand

The exponential scale length ($L_d$) of the Milky Way's (MW's) disk is a critical parameter for describing the global physical size of our Galaxy, important both for interpreting other Galactic measurements and helping us to understand how our Galaxy fits into extragalactic contexts.

• Unfortunately, current estimates span a wide range of values and often are statistically incompatible with one another.
• Here, we perform a Bayesian meta-analysis to determine an improved, aggregate estimate for $L_d$, utilizing a mixture-model approach to account for the possibility that any one measurement has not properly accounted for all statistical or systematic errors.
• Within this machinery we explore a variety of ways of modeling the nature of problematic measurements, and then employ a Bayesian model averaging technique to derive net posterior distributions that incorporate any model-selection uncertainty.