K.-L. Soon1*, T. Hanawa2, T. Muto3, T. Tsukagoshi1, M. Momose1
1 Ibaraki University, 2 Chiba University, 3 Kogakuin University* E-mail: kanglou.soon.sci@vc.ibaraki.ac.jp

SUMMARY
Aim: The properties of dust grains in protoplanetary disks are underdetermined. As a case study, we aim at revealing the dust properties and distribution in the crescent disk
surrounding HD 142527 by modeling.

Method: We use two-dimensional, axisymmetric disk models to reproduce the continuum emission at 890 µm from the disk of HD 142527 observed by ALMA during Cycle
0. Our model takes account of the dust scattering opacity and the disk geometry. We use two opacity models, the conventional model (conventional composition,homogeneous sphere, maximum grain size 1 mm) and the reduced-scattering model; the only different is the latter being 90% smaller in scattering opacity.

Results:• The conventional model cannot reproduce the 890 µm continuum emission in the disk northwestern region; the model intensity reaches a ceiling lower than theobserved value and it becomes insensitive to the increase in dust surface density due to the heavy scattering.
• With the reduced-scattering model, the emission is reproduced successfully in all azimuth direction, including the northwestern region.
• In the south region where the disk is optically thin, the best-fit parameters are found to be depending little on the scattering opacity.
• The contrast of dust surface density in the azimuth direction is derived to be about 40 in the reduced-scattering model, much smaller than that derived by theconventional model. which is 70 – 130.

Conclusion: The effective scattering might be lower than expected in protoplanetary disks.
Future Direction: Investigate the reason of low scattering, incorporate optical properties of porous dust aggregates, and perform multi-wavelength modeling.

1.

I N T R O D U C T I O N

3.

R E S U LT S

q NE: far side, SW: near sideq Inclination: 𝟐𝟕∘
q Fit radial intensity profile with𝟐
𝒓𝐨𝐛𝐬 − 𝒓𝟎,𝐨𝐛𝐬
𝑰𝐨𝐛𝐬 𝒓, 𝑷𝑨′ = 𝑰𝟎,𝐨𝐛𝐬 𝐞𝐱𝐩 −𝒘𝟎,𝐨𝐛𝐬

Near-IR

q The conventional model cannot
reproduce the intensity profiles in NW
due to the heavy dust scattering.
q The reduced-scattering model:• same 𝜿𝐚 , 90% smaller 𝜿𝐬 .
• estimates smaller 𝚺𝟎 , larger 𝒘𝟎 in
optically thick northern region.

𝑷𝑨′ = 𝑷𝑨 + 𝟏𝟗°
1” = 140 AU

890 µm50°

Figure 1:
1.6 µm, Fukagawa et al. 2006.

30°

Major axis
𝑷𝑨′ = 𝟎°

10°

350°

70°

Mid-IR

330°

90°

310°

110°

290°

130°

270°

150°

250°
170°

190°

Figure 8:
Derived best-fit (ΣH , 𝑤H , 𝑟H ). The conventional model cannot reproduce
the emission in 𝑃𝐴Y = 310∘ − 10∘ (gray shaded region).

4.

D I S C U S S I O N S

230°

210°

Major axis
𝑷𝑨′ = 𝟎°Far side𝑷𝑨′ = 𝟗𝟎°
Figure 2:18.72 µm (contour), 24.5 µm (color),
Verhoeff et al. 2011.

2.

Figure 3:890 µm continuum emission by ALMA Cycle 0, Fukagawa et al. 2013.

𝒓𝟎 = 𝟏𝟕𝟓 𝐚𝐮

M E T H O D

𝑷𝑨′ = 𝟐𝟕𝟎°

N

Near sideE

Figure 9:
Illustration of an axisymmetric, inclined, optically thick disk model.

18 𝑷𝑨′
intensity profiles

Figure 4:
Modeling flow chart.
Radiative transfer by M1 method,

𝒘𝟎 = 𝟐𝟕 𝐚𝐮

Input parameter𝚺𝟎 , 𝒘𝟎 , 𝒓𝟎NO

Criteriamet?

YES𝑷𝑨′Best-fit parameters

Figure 10:
Peak intensity against peak dust surface density, at different 𝑃𝐴′.

Conventional

Scattering-reduced

Kanno, Harada, & Hanawa (2013)

Criteria:

Calculate model
𝝆, 𝑻, 𝑱𝝂Ray tracing and beam
convolution

Compareintensity profile

Disk modelimage

q 2D, axis and midplane symmetric, passive disk
model in hydrostatic equilibriumq Dust radial surface density:𝒓 − 𝒓𝟎 𝟐
𝚺 𝒓, 𝑷𝑨′ = 𝚺𝟎 𝐞𝐱𝐩 −𝒘𝟎
q Dust grains properties:• compact sphere• silicate, carbonaceous compounds, water ice• solar elemental abundance• 𝒏 𝒂 ∝ 𝒂2𝟑.𝟓 , 𝒂𝐦𝐚𝐱 = 𝟏 𝐦𝐦
𝚺𝟎𝑰𝟎,𝐨𝐛𝐬 − 𝑰𝟎,𝐦𝐨𝐝≤ 𝟎. 𝟎𝟏 𝑰𝟎,𝐨𝐛𝐬𝒘𝟎,𝐨𝐛𝐬 − 𝒘𝟎,𝐦𝐨𝐝≤ 𝟏 𝐚𝐮𝒓𝟎,𝐨𝐛𝐬 − 𝒓𝟎,𝐦𝐨𝐝≤ 𝟏 𝐚𝐮Bright𝟗𝟎°𝟎°

Figure 5:
Dust opacity, Aikawa & Nomura (2006).

Dark

𝟐𝟕𝟎°

(𝑟H,IJK , 𝐼H,IJK )= 𝟎. 𝟏𝟎 𝐠 𝐜𝐦2𝟐

(𝑟H,PIQ , 𝐼H,PIQ )𝒘𝟎 = 𝟐𝟕 𝐚𝐮

𝑤H,IJK𝒓𝟎 = 𝟏𝟕𝟓 𝐚𝐮
𝑤H,PIQ𝝆𝟎 = 𝟏. 𝟑×𝟏𝟎2𝟏𝟔 𝐠 𝐜𝐦2𝟑

Figure 11:
The emissivity per unit length, 𝜅b + 𝜅K 𝜌𝑆e exp(−𝜏jIK ). 𝑆e is the source function and 𝜏jIK is the optical depth in the line of sight.

ALMA/45m/ASTE Users Meeting 2017, NAOJ , Mitaka, Japan (26 – 27 December 2017)
Figure 6:
Disk model example.

Figure 7:
Radial intensity profile example.

ACKNOWLEDGEMENT

This work is supported by MEXT KAKENHI Nos. 23103004, 24103504, and 26103702. This paper makes use of the following ALMA data:
ADS/JAO.ALMA#2011.0.00318.S. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together
with NRC (Canada), NSC and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA
Observatory is operated by ESO, AUI/NRAO, and NAOJ. Part of the data analysis was carried out on common use data analysis computersystem at the Astronomy Data Center of NAOJ.