THE STAR FORMATIONNEWSLETTER
No. 26(#1-5)

1. A Statistical Spectropolarimetric Study of Herbig Ae/Be Stars
2. Improved torque formula for low and intermediate mass planetary
migration
3. The shapes of column density PDFs - The importance of the lastclosed contour
4. Destruction of Refractory Carbon in Protoplanetary Disks
5. How do binary clusters form?

A Statistical Spectropolarimetric Study of Herbig Ae/Be Stars
K.M. Ababakr et al.

• 最もサンプル数の多いHa spectro-polarimetryデータ• 既存のデータ+新規17天体=>56天体のHAeBeサンプル• Ha polarization: 中心星近傍の円盤の証左• 3つのpolarization機構Spectropolarimetry of Herbig Ae/Be Stars 3• Depolarization• 強い連続波- polarized• 再結合線-unpolarized• HBeで多い• Line Polarization• 内側で生じたHαがdiskで散乱•

acc. shockなど• HAeやTTSで見られる• McLean効果

Figure 1. Schematic showing spectropolarimetry expectations across the Hα line in triplots (top) and (Q, U) diagrams (bottom). In the triplot, the Stokes
intensity (I) is shown in the bottom panel, polarisation (%) in the centre, while the position angle (PA) is shown in the upper panel. The first column showswhere the geometry of the circumstellar environment on the sky is circular and hence no line effect is detected. The other three columns show where thegeometry on the sky is not circular and a line effect is seen. The second column shows a depolarisation line effect, note that the depolarisation across Hα line
is as broad as Stokes I. This depolarisation line effect translates into (Q, U) diagram as a linear excursion from continuum knot towards the central line. The
arrows in the (Q, U) diagrams indicate the polarisation moves in and out of the line effect from blue to red wavelengths. Intrinsic line polarisation is shown inthird column, where Hα line from the accretion compact region is scattered in a rotating disk. In this case the polarisation across Hα is narrower that the widthof Stokes I and a flip is seen in PA caused by a rotating disk. This flip is seen as a loop in (Q, U) diagram. Finally column four shows a different polarisation
signature across the absorption component of Hα which is commonly known as the McLean effect. The figure is adapted from Vink et al. (2002).

• 中心星からの無偏光Hαが星周物質で吸収->再放射した一部が散乱偏光• 非対称成分があると偏光として見える• early Bは低検出率• B7-B8で偏光メカニズムが切り替わる• 後期側->磁気降着優勢• 早期側->Boundary Layer model?

• Line effectと相関なし• 上記は天体幾何にのみ依存

Spectropolarimetry of Herbig Ae/Be Stars

7

Improved torque formula for low and intermediate mass planetary migration
ed 2017 July 27; in original form 2017 April 25
M.A. Jimenez and F.S. Masset
ABSTRACTThe migration of planets on nearly circular, non-inclined orbits in protoplanetary discs
is entirely described by the disc’s torque. This torque is a complex function of thedisc parameters, and essentially amounts to the sum of two components: the Lindblad
torque and the corotation torque. Known torque formulae do not reproduce accurately
the torque actually experienced in numerical simulations by low- and intermediatemass planets in radiative discs. One of the main reasons for this inaccuracy is that theseformulae have been worked out in two-dimensional analyses. Here we revisit the torqueformula and update many of its dimensionless coefficients by means of tailored, threedimensional numerical simulations. In particular, we derive the dependence of theLindblad torque on the temperature gradient, the dependence of the corotation torqueon the radial entropy gradient (and work out a suitable expression of this gradient ina three-dimensional disc). We also work out the dependence of the corotation torqueon the radial temperature gradient, overlooked so far. Corotation torques are known
to scale very steeply with the width of the horseshoe region. We extend the expressionof this width to the domain of intermediate mass planets, so that our updated torqueformula remains valid for planets up to typically several tens of Earth masses, provided
these relatively massive planets do not significantly deplete their coorbital region. Our
torque expression can be applied to low- and intermediate-mass planets in opticallythick protoplanetary discs, as well as protomoons embedded in circumplanetary discs.
Key words: Planetary systems: formation – Planetary systems: protoplanetary discs

The shapes of column density PDFs - The importance of the last closed contour
J. Alves et al.

• log-normalなPDF形状はcompletenessによるものであり、より自然な定義を用いることでlog-normalピークは無くなりpower-law分布João Alves, Marco Lombardi, Charles J. Lada: Completeness limit of PDFsのみを示す。

• ‘last closedcontour’を定義とするのが良い

Herschel,Planck,2MASS[Lombardi+2015]• open contourは全質量(全領域)を正しくカバーしていない
Fig. 2. Column density map and respective PDF for a diﬀuse cloud (Polaris), a star formation poor cloud (Oph North), and astar forming rich cloud (Oph streamers). The red line on the map and on the PDF corresponds to the last closed contour while
the gray line corresponds to the peak of the PDF. The blue line represents the slope of the distribution above the completenesslimit. All maps cover about the same physical area of about 200 pc2 .

• 距離(分解能)に対しては不変, 空間構造(分布)には感度=>空間構造を調査するツールとして、まだPDFは使用可能

120 pc240 pc
480 pc960 pc1920 pc

120 pc240 pc
480 pc960 pc1920 pc

4.

103

102

5.

10110

• 正しくcompletenessを定義

Radomized pixels

104

Number of pixels

を持つ

Original

105

0101Log10(AK ) [mag]2101Log10(AK ) [mag]2Fig. 3. Left: Eﬀect of distance on the Oph Streamers PDF.
Right: Same, but with randomized pixel positions. The powerlaw PDF is invariant to distance (resolution), but not to thearrangement of cloud material.

したPDFはlog-normalでは•expected. We then computed the PDF of the two maps,
the original and the randomized one, for diﬀerent distances
なくpower-law分布(resolutions). Remarkably, as the distance (resolution) increases (decreases), the power-law slope of the PDF of theoriginal cloud remains essentially invariant to distance (res=>観測だけでなく理論研究もこの定義を用いるべきolution), while the PDF of the randomized cloud changes
dramatically. This implies that the column density PDF is
PDFの新しい物理解釈が必要 invariant to distance, but not to the spatial arrangement ofcloud material, and as such it may ultimately prove to bea useful tool for investigating cloud structure.

AckHedirres
res
StrlogusetrousedatReAbHAlv
AstABaM
Bea

Destruction of Refractory Carbon in Protoplanetary Disks
C grainのアバンダンス分布
D.E. Anderson et al.
6• 原始惑星系円盤中におけるrefractorycarbonのdepletionメカニズムの調査• 円盤表層による酸化or光分解• 表層のC grainとPAH• 円盤モデルを使った1+1D化学計算• T Tauri star, power-law disk
• >600 chemical species,~7000 reaction• ダストサイズ 0.01~10µm, (+10µm porous)• 光分解の方が外側まで有効, ダストサイズには弱く依存• 円盤寿命より早くdeplete99• midplaneのCは残る

Fig. 2.— Vertical cross-sections of the protoplanetary disk above the midplane demonstrating the refractory carbon abundance relative
to total hydrogen at 106 years for carbon grains with grain radii equal to 0.01 µm (a,b), 0.1 µm (c,d), and 10 µm with 96% porosity (e,f)
including oxidation (a,c,e) and UV photolysis (b,d,f).

=>vertical mixingが必要

• 円盤表層でCがdepleteする時間v.s.乱流でダストが表層に留まる時間=>円盤内側でdepleteが可能• 光分解~10au, 酸化<1au• 外側ではCは残る• 10-4 depletionを満たすのは、turbulentdisk(α=10-2)でも<1µmダストのケース=>小ダストでないとC depletionを説明できない
12

How do binary clusters form?
B. Arnold et al.
• バイナリクラスター生成のN体計算• クラスターはペアでしばしば見つかる• 単一クラスターより若いものが多い• 生成についてはよく分かっていない• KIRA integrator/STARLAB• N=1000, R=2pc, t=20Myr• NO gas/stellar evolution/external tidal field• IMFとconsistentな質量分布• 速度構造• inherited velocity (親;ランダム, 子;ランダム+相続) [Goodwin&Whitworth(2004)]• turbulent velocity field (パワースペクトルより)• 二つの初期状態パラメータOutcomes of H simulations

Microclusters

1.0SingleMergerBinary

0.8• 速度分布の違いによる影響
20=>速度コーヒーレンスの有無がバイナリ形成
z (pc)

Probability
Fraction

100.60−100.4にとても重要−200.20.00.30.5
Virial ratio αvir

0.7

Outcomes of M simulations
1.0
SingleMergerBinaryProbability
Fraction

0.8
0.6
0.4
0.2
0.0

0.3

0.5
Virial ratio αvir

0.7

Outcomes of S simulations
1.0Single
MergerBinaryProbability
Fraction

0.8
0.6
0.4
0.2
0.0

0.30.5
Virial ratio αvir

0.7

−20−10y( 0pc) 10• 初期状態との関係
2020100x (pc)−10−20• 最終分布に対し3つの構造を機械的に抽出• ビリアル比⤴でbinary fraction⤴
=>warmな領域の方が生成されやすい