Constraining dust extinction properties via the VVV survey

Abstract

Near-infrared color-excess and extinction ratios are essential for establishing the cosmic distance scale and probing the Galaxy, particularly when analyzing targets attenuated by significant dust. A robust determination of those ratios followed from leveraging new infrared observations from the VVV survey, wherein numerous bulge RR Lyrae and Type II Cepheids were discovered, in addition to BVJHKs(3:4 → 22) μm data for classical Cepheids and O stars occupying the broader Galaxy. The apparent optical color-excess ratios vary significantly with Galactic longitude (ℓ), whereas the near-infrared results are comparatively constant with and Galactocentric distance ( = = 1:49 ± 0:05 ( = 0:33 ± 0:02), whereas the O stars are expectedly impacted by emission beyond 3:6 μm. The mean optical ratios characterizing classical Cepheids and O stars are approximately ∼ 3:1 and ∼ 3:3, respectively.