2018MNRAS.475.5535I

We present the results of our UBVRI polarimetric observations of a dozen stars located close to the well-studied Bok globule Barnard 5 (B5), with several of the stars being seen through its outer layers (with A_V up to ∼3 mag). Using recent astrometric, spectroscopic and photometric surveys, we estimate the distance, spectral class and visual extinction for the observed stars and find that the results are in a good agreement with the available 3D extinction maps. We use a two-layer dust model of interstellar polarization towards B5, in which the layer closer to us is an extension of the Taurus cloud complex, and the farther one (including B5 and its halo) is related to the Perseus cloud complex (d ≃ 280-350 pc). Using spectral, photometric and polarimetric data on about 30 additional stars, we estimate the parameters of the former layer as λ_max ≃ 0.56 µm, P_max ≃ 0.7 per cent, θ ≃ 50°, A_V ≃ 0.7 mag, and show that the observed wavelength dependence of the position angle for the stars observed generally agrees with the two-layer model. We find that when the stars are seen through the globule layers with A_V = 2-3 mag, λ_max ≃ 0.6-0.8 µm, which differs significantly from the λ_max = 0.52-0.58 µm obtained by us for the diffuse interstellar medium in the direction of B5. We discuss the correlation of λ_max with the optical thickness into the globule as well as other correlations of the extinction and polarization parameters.