Abstract

Studying the interstellar medium (ISM) at high-galactic latitudes is of paramount importance for mitigating the impact of the dusty foreground when detecting a B-mode polarisation signal in the cosmic microwave background. Extinction serves as an invaluable tracer for the dusty ISM within the Galaxy. In this talk, we will delve into the challenges that arise when attempting to constrain extinction at high-galactic latitudes. I will demonstrate that in situations where extinction is low, complex, and multi-modal posterior distributions emerge due to degeneracies between extinction and other stellar features. Relying on a single point estimate for slight variations in extinction becomes unreliable and understanding extinction using photometry alone falls short of the mark. We will also show that using spectroscopically derived estimates of effective temperature can significantly reduce model degeneracies, thus narrowing down the posterior, but the posterior is highly dependent on the assumed measurement error.