Near-infrared imaging polarimetry of dusty young stars

Abstract

We have carried out JHK polarimetric observations of eleven dusty young stars, by using the polarimeter module IRPOL2 with the near-IR camera UIST on the 3.8-m United Kingdom Infrared Telescope (UKIRT). Our sample targeted systems for which UKIRT-resolvable discs had been predicted by model fits to their spectral energy distributions. Our observations have confirmed the presence of extended polarized emission around TW Hya and around HD 169142. HD 150193 and HD 142666 show the largest polarization values among our sample, but no extended structure was resolved. By combining our observations with HST coronographic data from the literature, we derive the J- and H-band intrinsic polarization radial dependences of TW Hya's disc. We find the disc's polarizing efficiency is higher at H than at J, and we confirm that the J- and H-band percentage polarizations are reasonably constant with radius in the region between 0.9 and 1.3 arcseconds from the star. We find that the objects for which we have detected extended polarizations are those for which previous modelling has suggested the presence of flared discs, which are predicted to be brighter than flat discs and thus would be easier to detect polarimetrically.