THE STAR FORMATIONNEWSLETTER
No. 289 (#26-30)
塚越崇(茨城大)3 Mar. 2017

1. Spiral-driven accretion in protoplanetary discs - III tri-dimensional
simulations
2. Probes of turbulent driving mechanisms in molecular clouds fromfluctuations in synchrotron intensity
3. Q+: Characterising the structure of young star clusters
4. Gaps in Protoplanetary Disks as Signatures of Planets: III.
Polarization
5. Binaries among low-mass stars in nearby young moving groups12Hennebelle et al.: Spiral-driven ac

Spiral-driven accretion in protoplanetary discs - III tri-dimensional simulations
P. Hennebelle et al.

• 星周infallがあるケースの3D計算• これまでの2Dを拡張[Lesur+2015]• RAMSESコードを使用(Cartesian coord.)• 特にspiral armの駆動に着目• 軸対称/非軸対称のexternal accretionを導入• ケプラー回転相当の比角運動量を持つ• 質量降着率は同一になるように• 非軸対称ケース• spiral armの生成 <- incoming flowによるもの• 円盤半径より外側でcumulated mass増加• log(r)<-1.2では時間変化なし=>質量が通過していない• α分布は変化なし=> no accretionと同じ振る舞い• infall rateを減らすとcumulated mass減少• 2D計算との比較 [Lesur+2015]• 3Dではαが大きめに出る=>αZのcontribution(Z軸の速度構造)• 軸対称accretion -> high-mのspiral armも対称• αは外側は非対称とcomparableだが、内側では減少• mass fluxも非対称と比べると小さくなる• accretion of non-rotating gas-> 円盤が早くshrink, spiral arm生成されず• 観測のspiral armは惑星よりinfalling motionでは

Probes of turbulent driving mechanisms in molecular clouds from fluctuations
in synchrotron
Synchrotron probes of turbulent driving.
intensity
C.A. Herron et al.

• 分子雲乱流の起源は様々• driving parameter ζで切り分ける• compressive, curl-free driving (ζ=0)• solenoidal, divergence-free driving(ζ=1)• シンクロトロン放射強度によってζの導出が可能か数値計算で調査• 3D MHD simulation• FLASH v4コードを使用, 256^3 cells• 初期はuniform gas density,
rho=6.56E-21 g/cm-3• L=2pc, B=10μG, T=10K, cs=0.2km/s• Herron+2016に倣って擬似観測

58Herron et al.

Q+: Characterising the structure of young star clusters
racterising
S.E. Jaffa ettheal. structure of young star clusters• いままで用いられて来たQパラメータから発展させ、3つのパラメータを用いてA. P. Whitworth,
O. Lomax
クラスターのフラクタル形状を調べる新しいアルゴリズムを紹介

nd Astronomy, Cardi↵ University, Cardi↵ CF24 3AA, Wales, UK• the fractal dimension D; 分布がclumpyかsmoothかを決める• the number of levels L; cloud中のsubstructureのスケールを決める• the density scaling exponent C; 異なるスケール間の質量の相対分布を決める
ABSTRACT

Many young star clusters appear to be fractal, i.e. they appear to be concentrated in anested hierarchy of clusters within clusters. We present a new algorithm for statisticallyanalysing the distribution of stars to quantify the level of sub-structure. We suggest
that, even at the simplest level, the internal structure of a fractal cluster requires
the specification of three parameters. (i) The 3D fractal dimension, D, measures theextent to which the clusters on one level of the nested hierarchy fill the volume of
their parent cluster. (ii) The number of levels, L, reflects the finite ratio between thelinear size of the large root-cluster at the top of the hierarchy, and the smallest leafclusters at the bottom of the hierarchy. (iii) The volume-density scaling exponent, C =d ln[ n]/d ln[L] measures the factor by which the excess density, n, in a structure ofscale L, exceeds that of the background formed by larger structures; it is similar, but
not exactly equivalent, to the exponent in Larson’s scaling relation between density
and size for molecular clouds. We describe an algorithm which can be used to constrain
the values of (D, L, C) and apply this method to artificial and observed clusters. We
show that this algorithm is able to reliably describe the three dimensional structure ofan artificial star cluster from the two dimensional projection, and quantify the varied
structures observed in real and simulated clusters.

Gaps in Protoplanetary Disks as Signatures of Planets: III. Polarization
H. Jang-Condell• Gap有り/無し円盤の見え方をinclination angleを変えて計算• total intensityとpolarized intensity (at 1µm)の違いに着目
Table 1. Gap parameters for given• 円盤モデル詳細はPaper 1 [Jang-Condell 2008,2009]planet masses.

• M*=1M⦿, R*=2.6R⦿, Teff=4280K• Macc=10-8 M⦿/yr, α=0.01, N(a)∝a-3.5 (0.005µm-1mm)• ガウシアン型ギャップ• self-consistent RT for density & temperature structures• face-on diskの振る舞い• ギャップなしはfractionがほぼ一定(rに伴いやや減少)• ギャップ位置でIもPIも減少し、outer edgeでピーク=>scattering angleではなく、一回/多重散乱の強度の比率で決まる(多重散乱のほうが効く)• outer edgeではtotal brightness増大
fractional pol.は減少

Planet mass1

gap width (w/a)

gap depth (d)72 M (0.23 MJup )210 M (0.65 MJup )

0.11
0.17

0.56
0.84

1 Actual masses used for this work. In the text, the masses
have been rounded to 70 and 200 M

for convenience.

gap parameters are shown in Table 1 and are calculated
based on viscous gap opening simulations by Bate et al.
(2003) and Crida et al. (2006). The gaps are partiallycleared, in that the vertically integrated surface densityof the disk is decreased by no more than 60% for themost massive planet modeled. The gaps are modeled as
Gaussian perturbations of the form⌃(r) = ⌃0 (r) 1

d exp[ (ra)2 /(2w2 )] .

(1)

where ⌃0 is the unperturbed surface density profile, d isthe depth of the gap, a is the gap position, and w is thegap width. For a full discussion of the relationship between planet mass, disk properties, and gap parameters,
see Paper I.
2.2. Polarized Scattered Light=>IでもPIでもギャップ位置は決まるが、PIのみ As shown in Paper II, the scattered light brightness ofではギャップのコントラストを過小評価する

the disk surface, assuming single isotropic scattering, is
I1s (⌫) =!⌫ µR⇤2 B⌫ (T⇤ )2,(2)• 傾いた惑星なし円盤• 等輝度線は楕円でよくフィットするが、中心は星位置とずれる
no planet• 円盤上層の散乱光を見るため• PIのほうが顕著• anisotropy in P fractionのため• 傾いた惑星ギャップ円盤

70Mearth• 見かけのギャップ幅が実際とは異なる• minor axisでギャップ幅が狭く見えるは11. Model images of a gap-less disk observed in scattered total and polarized light at 1 µm at varying inclinations
ずだが、PIでは逆になる
200M
earth
Columns are arranged the same as in Figure 1. From top to bottom: 15 , 30 , 45 , 60 , and 75 inclination. The
are tilted so that the top side of the image is the far side of the disk. In the I and P images, white contour=>円盤がwarpしているように見えるdisks
show isophotes and black dashed lines show best-fit ellipses to those isophotes. Isophotes are chosen to have maximum
Figure 3θ1 = π/2 − β + i

radius of 5, 10, 15, and 20 AU. In the f images, solid, dotted, and dashed contours show f values of 0.5, < 0.5, and> 0.5, respectively. The values of the contours are indicated on the color scale bar.
• ギャップのminimum & imaximaは楕円でよくβフィットできる(IおよびPIどちらも). Same as Figure 3, for a disk with a partial gap cleared by a 70 M planet. The isophotes here trace the=>ギャップの存在を調べるのに有用
to observerlevel equal to half the brightness of the brightened gap edge along the minor axis toward the far edge obrightness
riFigure 4dthe disk. The two inner contours bracket the gap trough, while the two other ones bracket the brighten far edge othe gap.

• total intensityはnear sideで常に強いが、pol.
iβrd
θ2 = π/2 − β − ifractionはnear sideで低くなる=>near/farはPIではなくpol. fractionで見ることが大事Figure 9.

Figure 5.

Illustration of scattering angles from opposite
side of an inclined disk. The disk is inclined at an angle
i and the opening angle of the disk is
at a distancerd from the star. Light is scattered o↵ the disk surface
toward the observer in a non-symmetric fashion because

Same as Figure 4, for a disk with a partial gap cleared by a 200 M

planet.

Binaries among low-mass stars in nearby young moving groups
M. Janson et al.

• moving groupにあるlate-typeはまだpre-main sequenceであり、isochronによるクラスター年齢推定に有用• isochronに使われるMstar(Teff)-L*はモデル依存するため不定性大• late-typeは特にモデルの不定性が大きい• バイナリであれば、モデルを介さず星質量の直接導出が可能=> 近傍moving groupにある低質量星の高分解能観測を実行
M. Janson et al.: Young• 61/181天体で伴星を検出, 38天体は新検出=>カタログ化
詳細な物理量導出などはbeyond the scope′thgi
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