星形成ゼミ 論文紹介 2012/11/16
Star Formation Newsletter No.238
担当：小屋松1. The Protocluster G18.67+0.03: A Test Case for Class I CH3OH Masers as EvolutionaryIndicators for Massive Star Formation
C.J. Cyganowski, C.L. Brogan, T.R. Hunter, Q. Zhang, R.K. Friesen, R. Indebetouw, C.J. Chandler【目的】Class I メーザーは大質量星の進化の指標として使えるか？
【観測】SMA および VLA によるミリ波観測
・G18.67+0.03 ̶EGOs サーベイで 3 つの Class I CH3OH メーザー源(EGO, UCHII, NEMS)【結果】・3 つすべてのメーザー源に 13CO アウトフローが付随
Cyganowski et al.
・EGO, NEMS
6.7GHz Class II CH3OH メーザー, SiO(5–4)放射→活発なアウトフローにより Class I メーザーが励起
・UCHIIClass II メーザー, SiO 放射ともになし→13CO はアウトフローの残骸【結論】Class I CH3OH メーザーは若い領域(hot core)と進化の進んだ領域(UCHII)の両方で励起される

2. Discovery of Two New Class II Methanol Maser Transition in G 345.01+1.79
S.P. Ellingsen, A.M. Sobolev, D.M. Cragg, and P.D. Godfrey【目的】新たな Class I CH3OH メーザーの遷移を発見する【観測】Swedish ESO Submillimeter Telescope (SEST)・G345.01+1.79 ̶Class II CH3OH メーザー源
・既知 7 本+予測 6 本の Class II CH3OH メーザー遷移【結果】13 本中 9 本の遷移を検出
・2 本が初検出
13-3–12-4 E …104.1 GHz5-1–42 E…216.9 GHz→Class II CH3OH メーザーのシリーズが 10 個遷移が 18 本にそれぞれ増えた2Federrath & Klessen2011) regulate star formation. In this picture, turbulent
energy stabilizes the clouds on large scales, but at thesame time, supersonic turbulence induces local compressions,Formation
producing filaments
and ofcores,
which are theMagnetizedpro3. The Star
RateTurbulent
Clouds: Comparing Theory,
genitors of stars. Eventually, both turbulence and mag-Simulations, and Observations

Christoph Federrath, and Ralf S. Klessen【目的】星形成率を決めるパラメータは何か？
【手法】・星形成率の 6 つの理論モデルKrumholz & McKee
Padoan & Nordlun
Hennebelle & Chabrierの 3 つとこれらの multi-freefall 版
・MHD シミュレーション
・系内の分子雲の観測値を比較【結果】・星形成率は 4 つのパラメータに依存・パラメータの分散により観測の分散が説明できる
・マッハ数と乱流の強さが最も重要なパラメータ・磁場も二次的に効いてくる

4. Evidence for Grain Growth in Molecular Clouds: A Bayesian Examination of theExtinction Law in Perseus
Jonathan B. Foster, Kaisey S. Mandel, Jaime E. Pineda, Kevin R. Covey, Héctor G. Arce, Alyssa A. Goodman【目的】減光則をよりよく求める【手法】Megacam r, i, z-band と UKIDSS J, H, K-band を組み合わせて背景光の色を測定
階層ベイズ統計モデル
・測定値の誤差
・もともとの色のばらつき
・スペクトル型・ダスト赤化を考慮して個々の星と集団の特徴のパラメータを同時に推定【結果】減光 AV と減光則の傾き RV とに強い相関
他の領域と同じ傾向→ダスト成長はユニバーサルな過程である

5. The Absence of Cold Dust around Warm Debris Disk Star HD 15407A
Dideaki Fujiwara, Takashi Onaka, Satoshi Takita, Takuya Yamashita, Misato Fukagawa, Daisuke Ishihara, Hirokazu
Kataza, and Hiroshi Murakami【目的】デブリ円盤の冷たいダストの量を求める【観測】Herschel/PACS 70µm, 100µm, 160µm および AKARI/FIS WIDE-S(90µm)【結果】MIR のフィットの外挿で FIR 超過も説明できる→FIR の起源は内側の温かいダスト(~500–600K)で外側の冷たいダスト(~50–130K)は存在しない
Ldust/L*~0.005 は大きすぎて定常モデルでは説明できない
・2 つの非定常メカニズム
Late Heavy Bombardment (LHB)
Two-body Impact
たくさんの衝突天体を要する LHB シナリオでは冷たいダストが受かるはず
The AstrophysicalJournal Letters, 759:L18(5pp), 2012 November 1
Fujiwara et al.
→LHB
では HD15407Aのデブリ円盤を説明できない
10

Flux Density (Jy)

12MASSWISE
AKARI/IRC
Subaru/COMICSAKARI/FIS
Herschel/PACS
IRAS
Spitzer/IRS
Star
Star+BB(505K)

0.1

0.01

110
Wavelength (µm)

100Figure 1. NIR–FIR SED of HD 15407A. The black crosses indicate the 2MASS photometry, which determines the photospheric contribution of the star (Kurucz1992) shown as the gray solid line. The purple, blue, green, and yellow filled circles, and black open circles indicate the photometric data of WISE, AKARI/IRC,
Subaru/COMICS, and AKARI/FIS, and IRAS, respectively. The red open and filled circles indicate the photometric measurements from individual images taken with
Herschel/PACS and their weighted-average of photometry for each band, respectively. All of the flux densities are not color-corrected. The vertical and horizontal
bars of the photometric data show the flux density errors and the bandwidths, respectively. The orange solid and gray dashed lines indicate the Spitzer/IRS spectrum
and the estimated continuum level of the excess emission, respectively, taken from Fujiwara et al. (2012a).

3.2. Mass of Warm Debris around HD 15047A
Fujiwara et al. (2012a) estimated the mass of fine warm dust
around HD 15407A to be 7 × 1017 kg ∼10−7 M⊕ from thedust model fitted to the band features seen in the Spitzer/IRSspectrum at 5–35 µm. This value does not include the mass ofthe blackbody dust, which consists of large (!10 µm in size)
grains and rubble.
Assuming that the continuum component of the observed
excess emission at MIR and FIR wavelengths is attributable toblackbody grains of 505 K at Rdust = 0.6 AU, as suggested by
Fujiwara et al. (2012a) and this work, and that its flux density
is proportional to the sum of geometrical cross sections of thedust with the grain size distribution of n(a) ∝ a −3.5 , we could
estimate the total mass of large debris dust as!
"!
"!
"1MtotalLdustρamin 2= 2.7 × 10−4M⊕L∗
2.5 g cm3µm" 12 !
"2!

∼5×10−5 M⊕ ∼ 3×1020 kg assuming amax = 1 mm. Assuming
amax = 1 km, the total mass is estimated to be ∼0.05 M⊕∼3 × 1023 kg, corresponding to a few lunar masses or about
half of Mars’ mass.
An upper limit on the mass of cold dust (∼50 K at Rdust =60 AU) around HD 15047A could also be estimated in thesame manner from the upper limit on the fractional luminosity
Ldust /L∗ " 2 × 10−6 set by the present work. Assuming thesame grain size distribution (n(a), amin , amax ) as that of warm
dust, an upper limit on the mass of cold dust is given as just afew times of the mass of warm dust as estimated above.
3.3. NIR Excess
As mentioned in the previous subsection, no debris material colder than ∼500 K is suggested by the MIR–FIR SEDof HD 15407A. On the other hand, photometry at 4.6 µm in
the WISE W2 band shows excess over the estimated continuum
component of blackbody (Figure 1), suggesting the presence