Lyα Radiative Transfer: A Stokes Vector Approach to Lyα Polarization

Ly-alpha emitting galaxies and giant blobs (LABs) have been extensively observed to study the formation history of galaxies. However, origin their extended emission, especially LABs, remains controversial. Polarization signals from some LABs discovered, this is commonly interpreted as strong evidence supporting that emission originates resonance scattering. The Monte Carlo radiative transfer code LaRT updated investigate polarization using Stokes vector formalism. We apply a few models explore fundamental properties Ly-alpha. Interestingly, individual photon packets are found be almost completely polarized by sufficient number scatterings (N_scatt > 10^4-10^5 in static medium) or Doppler shifts induced gas motion, even starting unpolarized light. It also pattern can exhibit non-monotonically increasing cases, besides commonly-known trend monotonically increases with radius. primarily determined degree anisotropy radiation field, which eventually controlled medium's optical depth velocity field. If once achieve ~100% polarization, radial profile appears correlate surface brightness profile. A steep tends yield rapid increase linear near source location. In contrast, shallow gives rise slowly pattern.