Ian W. Stephens

Inclination-induced polarization of scattered millimetre radiation from protoplanetary discs: the case of HL Tau

Spatially resolved polarized millimeter/submillimeter emission has been observed in the disk of HL Tau and two other young stellar objects. It is usually interpreted as coming from magnetically aligned grains, but can also be produced by dust scattering, as demonstrated explicitly by Kataoka et al. for face-on disks. We extend their work by including the polarization induced by disk inclination with respect to the line of sight. Using a physically motivated, semi-analytic model, we show that the polarization fraction of the scattered light increases with the inclination angle

THE GALACTIC MAGNETIC FIELD'S EFFECT IN STAR-FORMING REGIONS

i

STELLAR CLUSTERINGS AROUND “ISOLATED” MASSIVE YSOs IN THE LMC

, reaching

LINKING DENSE GAS FROM THE MILKY WAY TO EXTERNAL GALAXIES

1/3

SPITZER OBSERVATIONS OF DUST EMISSION FROM H II REGIONS IN THE LARGE MAGELLANIC CLOUD

for edge-on disks. The inclination-induced polarization can easily dominate that intrinsic to the disk in the face-on view. It provides a natural explanation for the two main features of the polarization pattern observed in the tilted disk of HL Tau (

TESTING MAGNETIC FIELD MODELS FOR THE CLASS 0 PROTOSTAR L1527

i \sim 45^\circ

Scattering-produced (sub)millimetre polarization in inclined discs: optical depth effects, near–far side asymmetry and dust settling

): the polarized intensity concentrating in a region elongated more or less along the major axis, and polarization in this region roughly parallel to the minor axis. This broad agreement provides support to dust scattering as a viable mechanism for producing, at least in part, polarized millimeter radiation. In order to produce polarization at the observed level (

ALMA Observations of Polarization from Dust Scattering in the IM Lup Protoplanetary Disk

\sim 1\%

ALMA Reveals Transition of Polarization Pattern with Wavelength in HL Tau’s Disk

), the scattering grains must have grown to a maximum size of tens of microns. However, such grains may be too small to produce the opacity spectral index of

1.3 mm Polarized emission in the circumstellar disk of a massive protostar

\beta \lesssim 1