The Panchromatic Hubble Andromeda Treasury XV. The BEAST: Bayesian Extinction and Stellar Tool

TL;DR

The BEAST is a probabilistic tool that models stellar spectral energy distributions and dust extinction simultaneously, accounting for observational uncertainties, to derive stellar properties from large multi-band resolved star surveys.

Contribution

It introduces a Bayesian framework that incorporates complex dust extinction models and measurement covariances, improving the analysis of resolved stellar populations.

Findings

Accurately infers stellar properties from Hubble data.

Effectively constrains line of sight dust extinction.

Handles measurement uncertainties and covariances robustly.

Abstract

We present the Bayesian Extinction And Stellar Tool (BEAST), a probabilistic approach to modeling the dust extinguished photometric spectral energy distribution of an individual star while accounting for observational uncertainties common to large resolved star surveys. Given a set of photometric measurements and an observational uncertainty model, the BEAST infers the physical properties of the stellar source using stellar evolution and atmosphere models and constrains the line of sight extinction using a newly developed mixture model that encompasses the full range of dust extinction curves seen in the Local Group. The BEAST is specifically formulated for use with large multi-band surveys of resolved stellar populations. Our approach accounts for measurement uncertainties and any covariance between them due to stellar crowding (both systematic biases and uncertainties in the bias) and absolute flux calibration, thereby incorporating the full information content of the measurement. We illustrate the accuracy and precision possible with the BEAST using data from the Panchromatic Hubble Andromeda Treasury. While the BEAST has been developed for this survey, it can be easily applied to similar existing and planned resolved star surveys.