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 (<E(J - 3:5 μm)=E(J - Ks)i = 1:28 ± 0:03). The results derived imply that classical Cepheids and O stars display separate optical trends (RV;BV ) with ℓ, which appear to disfavor theories advocating a strict and marked decrease in dust size with increasing Galactocentric distance. The classical Cepheid, Type II Cepheid, and RR Lyrae variables are characterized by <AJ=E(J - Ks)> = <RJ;JKs > = 1:49 ± 0:05 (<AKs =AJ> = 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 <RV;BV > ∼ 3:1 and <RV;BV > ∼ 3:3, respectively.
Áreas temáticas de ASJC Scopus
- Astronomía y astrofísica
- Ciencias planetarias y espacial