Millimeter-wave polarization of protoplanetary disks due to dust scattering

Journal Article · Mon Aug 10 04:00:00 EDT 2015 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/809/1/78· OSTI ID:22882786

Kataoka, Akimasa; Dullemond, Cornelis P ^[1]; Muto, Takayuki ^[2]; Momose, Munetake; Tsukagoshi, Takashi ^[3]; Fukagawa, Misato ^[4]; Shibai, Hiroshi ^[5]; Hanawa, Tomoyuki ^[6]; Murakawa, Koji ^[7]

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1. Institute for Theoretical Astrophysics, Heidelberg University, Albert-Ueberle-Strasse 2, D-69120 Heidelberg (Germany)
2. Division of Liberal Arts, Kogakuin University, 1-24-2 Nishi-Shinjuku, Shinjuku, Tokyo 163-8677 (Japan)
3. College of Science, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512 (Japan)
4. National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan)
5. Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043 (Japan)
6. Center for Frontier Science, Chiba University, 1-33 Yayoi-cho, Inage, Chiba 263-8522 (Japan)
7. College of General Education, Osaka Sangyo University, 3-1-1, Nakagaito, Daito, Osaka 574-8530 (Japan)

We present a new method to constrain the grain size in protoplanetary disks with polarization observations at millimeter wavelengths. If dust grains are grown to the size comparable to the wavelengths, the dust grains are expected to have a large scattering opacity, and thus the continuum emission is expected to be polarized due to self-scattering. We perform 3D radiative transfer calculations to estimate the polarization degree for the protoplanetary disks having radial Gaussian-like dust surface density distributions, which have been recently discovered. The maximum grain size is set to be 100 μm and the observing wavelength to be 870 μm. We find that the polarization degree is as high as 2.5% with a subarcsec spatial resolution, which is likely to be detected with near-future ALMA observations. The emission is polarized due to scattering of anisotropic continuum emission. The map of the polarization degree shows a double-peaked distribution, and the polarization vectors are in the radial direction in the inner ring and in the azimuthal direction in the outer ring. We also find the wavelength dependence of the polarization degree: the polarization degree is the highest if dust grains have a maximum size of a{sub max}∼λ/2π, where λ is the observing wavelength. Hence, multi-wave and spatially resolved polarization observations toward protoplanetary disks enable us to put a constraint on the grain size. The constraint on the grain size from polarization observations is independent of or may be even stronger than that from the opacity index.

• OSTI ID: 22882786
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 809; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United Kingdom
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ANISOTROPY
COMPARATIVE EVALUATIONS
COSMIC DUST
DENSITY
DISTRIBUTION
EMISSION
FREQUENCY DEPENDENCE
OPACITY
POLARIZATION
PROTOPLANETS
RADIANT HEAT TRANSFER
SPATIAL RESOLUTION
SURFACES