Comparison of contrasts. Contrast performance limited by the speckle noises (bold solid lines) and by the photon noise (dashed lines) is compared with ΔPC_p/s (filled circles), that is, contrast of the polarized feature signal. a) a “typical” planet with averaged properties of the observable planets with g = 1.0. b) same as a) except for g = 0.05. c) Gliese 876 b with g = 1.0. d) Gliese 876 b with g = 0.05. The thin solid line in each panel is ΔPC_p/s(θ) for a planet with the same radius. The polarization feature is detectable in the ranges of θ designated by the arrows. 3-sigma C_det (dashed-dotted lines) and C_raw (dotted lines) are also plotted for the reference.