#316 (No. 28 – 37)

平野 信吾 (九州大学)

The Star Formation Newsletter

2019/06/07

28 On the origin of very massive stars around NGC 3603

29 Effect of Different Angular Momentum Transport Mechanisms on theDistribution of Water in Protoplanetary Disks
30 Millimeter-wave polarization due to grain alignment by the gas flow inprotoplanetary disks

31 Stellar encounters with giant molecular clouds
32 The Core Mass Function in the Infrared Dark Cloud G28.37+0.07
33 Widespread Molecular Outflows in the Infrared Dark Cloud
G28.37+0.07: Indications of Orthogonal Outflow-Filament Alignment
34 Close companions around young stars
35 Exploring the dimming event of RW Aur A through multi-epoch VLT/XShooter spectroscopy
36 The Origins of Protostellar Core Angular Momenta
37 Modeling Sulfur Depletion in Interstellar Clouds

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1大質量星 (Very Massive Star, VMS, with Mstar > 100 [Msun]) の形成メカニズム➢ 星団形成 (fragmentation of the core)➢ 単独星形成 (monolithic collapse) → 星形成領域から脱出した孤立した/若い/大質量星⚫ (LMC) VMSs at >25 pc from the starburst cluster R136 at the heart of 30 Doradus⚫ (MW) Two field VMSs (RFS7, RFS8) at > 50 pc from the star-forming region NGC3603
http://adsabs.harvard.edu/abs/2019A%26A...625L...2K

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2

RFS7 (O2.5If/WN6) and RFS8 (O3.5If) (Roman-Lopes et al. 2016)⚫ 若い大質量星 (~ 100 [Msun])⚫ 星形成領域 NGC3603 young cluster (YC) の中心から > 50 [pc] に位置する⚫ 周囲 2 [pc] に他の星形成は見られない(今回) Gaia Release 2 (DR2) catalogueを用いて形成元を調べる➢ 座標 (NGC3603からの距離)➢ 固有運動 (遡って形成領域を特定する)
NGC3603周りの相対固有運動 (ミリ秒/年)

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3

Bow-shock-shaped
structure
approximately 1 pc
from RFS7, with alength of ∼5 pc➔ RFS7 is a runaway
star from NGC3603.

No evidence for a bow
shock around RFS8
➔ RFS8 is not (?)

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4

RFS7 … young (~ 1Myr) & massive (~100 Msun) O2.5If/WN6 star
⚫ NGC3603 の中心から ~ 53 [pc] に位置⚫ 高速で運動し、バウショックを伴う⚫ NGC3603 から 1-2 Myr前に弾き飛ばされたと考えられる⚫ (疑問) NGC3603は ~100 [Msun]の星を力学的に弾き出せるか
RFS8 … young (~2 Myr) & massive (~70 Msun) O3.5If star
⚫ NGC3603 の中心から ~ 59 [pc] に位置⚫ バウショックが見られない (周囲にまだ星雲が残っていて、ダスト放射が飽和)⚫ NGC3603 で形成されたものではない⚫ RFS8の近傍には、形成領域となりうる星団は見つからなかった⚫ (不定性) age, astrometric, radial velocity を将来観測でアップデートする必要がある29

5

http://adsabs.harvard.edu/abs/2019ApJ...875...43K

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7

http://adsabs.harvard.edu/abs/2019ApJ...874L...6K

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St > 1St ~ 1
δvr < δvΦSt < 1

δvr > δvΦδvr ~ δvΦ8

31 Stellar encounters with giant molecular clouds
Giorgi Kokaia, Melvyn B. Davies

http://adsabs.harvard.edu/doi/10.1093/mnras/stz813

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31 Stellar encounters with giant molecular clouds
Giorgi Kokaia, Melvyn B. Davies“Galactic Habitable Zone (GHZ)”• is an annular region in the Galaxy
in which one is most likely to find ahabitable planet.
• The outer edge ... minimum
metallicity ([Fe/H] > −0.7), which
can sustain complex life becomes
impossible.
• The inner edge ... maximum
metallicity, to avoid a higher
occurrence rate of gas giants, thiscan inhibit the chances of forming
terrestrial planets in the habitablezone.
• Additional conditions …

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11

http://adsabs.harvard.edu/abs/2019ApJ...873...31K

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[本研究] CMF in a massive IRDC, G28.38+0.07 (以下 G28)
⚫ IRDC G28 … 遠方 (5 kpc), 大質量 (105 Msun) 分子雲⚫ 先行研究より、原始星降着・フィードバック現象が進行中であることは確認済。
ALMA Cycle 3 : project 2015.1.00183.S (PI: Kong)⚫ 46 12m antennas, C40-4 configuration
コア特定➢ グラフ理論に基づいた手法 (“astrograph”)
Crowded regionにおけるコア特定が得意➢ 系統樹的手法 (“astrodendro”; Cheng et al. 2018)➢ (参照) Zhang et al. (2015)

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astrpgraph (グラフ理論)
astrodendro (系統樹)Zhang et al. (2015)

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astrpgraphastrodendro

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原始星からのジェット/アウトフローは降着円盤の回転軸に揃う➔ “accretion-filament correlation” の証拠を得るため、アウトフローとフィラメントの間の角度を調べる

http://adsabs.harvard.edu/abs/2019ApJ...874..104K

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[先行観測] Stephenes et al. (2017)⚫ Perseus分子雲の57の原始星 → random 分布 (乱流降着起源で説明)[理論研究] Li et al. (2018)⚫ Mostly orthogonal outflow-filament orientation in massive infrared dark clouds (IRDCs)[本研究] IRDC G28.37+0.07 (G28)⚫ massive (105 Msun) IRDC
⚫ “dark” cloud = extremely early evolutionary stage of star formation⚫ CO bipolar outflowsの方向は ”ALMA CO(2-1) data” を用いて決定⚫ 一部は SiO(5-4) line データを使い角度決定を補正⚫ Filamentは “8 μm Spitzer GLIMPSE survey” のイメージデータを使って決定⚫ 一部は “1.3mm ALMA continuum” データも利用

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Orthogonal to theparent filament

34 Close companions around young stars
Marina Kounkel et al.

http://adsabs.harvard.edu/abs/2019A J....157..196K

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19

http://adsabs.harvard.edu/abs/2019A%26A...625A..49K

35“bright state”

Observation by the VLT/X-Shooter“dim state”

3 majordimmingevents

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http://adsabs.harvard.edu/abs/2019ApJ...876...33K

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No initial bulk rotation

For 4 intermediate-resolution (Ncell=5123)
and 9 high-resolution (Ncell=10243) runs22

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S (硫黄)

欠乏

http://adsabs.harvard.edu/abs/2019A%26A...624A.108L

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