GREX-PLUS：
マゼラン雲の星形成・星間物質のサイエンス
下西 隆（新潟大学）
光赤天連シンポジウム, 2022.7.13 オンライン

大マゼラン雲 (のどこか)

Credit: NASA

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The Large and Small Magellanic CloudlNearest star-forming galaxies—dLMC/SMC = 50/60 kpc1 ( 1” = 0.25/0.3 pc)—nearly face-on2 (LMC, i ~35°)
lLow metallicity3—LMC : ~1/2-1/3, SMC : ~1/5-1/10 of solar
neighborhood=> Excellent laboratory to study interstellar
chemistry at decreased metallicity

LMCSMC

1Alves, 2004, 2Westerlund, 1990, 3Luck et al. 1998

Fig.1 Optical images of the LMC and SMC[Ref. E. Slawik (LMC), A. Nota/ESA, STScI (SMC)]

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SAGE (Spitzer) & HERITAGE (Herschel) [PI. M. Meixner]
LMC

3.6 µm
8.0 µm160 µmSMC

l Photometry: 3.6, 4.5, 5.8, 8.0, 24, 70, 160 µm (Spitzer/IRAC,MIPS; Meixner+ 2006, Gordon+ 2011), 100, 160, 250, 350, 500 µm(Herschel/PACS, SPIRE; Meixner+ 2010, 2013)l Spatial resolution: 2”~40”[~60 (LMC) / 30 (SMC) deg2 area]l Spectroscopy (Spitzer/IRS): 5–37 µm, R=60-600, slit width =4”-11”, ~2000 sources (Kemper+ 2010, Woods+ 2011)
Fig.2 Three-color images of the LMC/SMC. Red: 3.6 µm, Green: 8.0 µm, Blue: 160 µm[constructed based on the SAGE/HERITAGE archival data at IPAC]

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LSLMC (AKARI) [PI. T. Onaka]

10’7.0,(= 11,15015,pc)24 µm (Ita+ 2008, Kato+ 2012)l Photometry: 3.2,—650,000 (3µm) and 52,000 sources (24µm), limit = 24µJy (3µm)
Fig.3
AKARI
three-color
image of the LMC
lSpatial
resolution:4”~10”(Blue: 3 µm, Green: 7 µm, Red: 15 µm)[~10 deg2 area, 600 pointing]l Spectroscopy: 2.5–5 µm, R=15-40, slitless, ~1750 sources in thecatalog (Shimonishi+ 2013)

3 µm
7 µm
15 µm

Infrared Spectra obtained by AKARI LSLMC
年老いた星(酸素星)

生まれたばかりの星(原始星)

ただただ赤い天体

酸素系分子ガス
氷バンド
PAH
水素輝線

炭素系分子ガス

炭素系分子ガス
Wavelength [µm]

年老いた星(炭素星)

激しい質量放出をしている炭素星

Fig.4 Classification of LSLMC sources based on their NIR spectra [Shimonishi+ 2013]

???
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GREX-PLUS Survey of the Magellanic Clouds
10s sensitivity—: GREX-PLUS img (20min)---: GREX-PLUS spec (R=30,000, 20min)---: JWST spec (R=1000-3000, 30min)—: VMC img

10000
1000

—: AKARI LSLMC img---: AKARI LSLMC spec (R=30)—: Spitzer SAGE img (10s)---: Spitzer IRS spec (R=100, 30min)—: Embedded High-mass YSO (ST16)—: Embedded Low-mass YSO (Elias 29)—: Herbig Ae/Be (AB Aur)—: T Tauri Disk (AA Tau)
at 50 kpc

Flux [mJy]

100
101
0.1
Fig.5 Sensitivities andwavelength coverages of theLMC observations by AKARI,Spitzer, JWST, and GREXPLUS

0.01
0.001
0.0001
Wavelength [µm]6/10GREX-PLUS Observations of YSOs in the LMC/SMCl GREX-PLUS will detect all most all ofsolar-mass YSOs in the MCs
AKARI/IRC, Spitzer/IRS (5 µm)(10s, R ~30-100)

GREX-PLUS (SPEC)(20 min, 10s, R ~30,000)

NumberIMF(Kroupa+ 01)

0.6’’=0.15pc

3.6 µm flux [mJy]

JWST/NIRSpec IFU(10 min, 10s, R ~1000)

LMC(50kpc)

GREX-PLUS (IMG)(20 min, 10s)
TAO/MIMIZUKU(15 min, 10s)

Mass (Msun)
Fig.6 Mass distribution histogram for YSOs
in the LMC [Whitney+ 08].

Fig.7 Predicted flux and color of YSOs in the LMC(Based on the YSO model by Robitaille et al. 2008)

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High-resolution MIR Spectroscopy of Massive YSOsl Various molecular absorption lines
are seen in the MIR region ofmassive YSOs*—H2O, CO2, C2H2, HCN, CH4, NH3,etc.
—They arise from hot gas in thevicinity of the protostar (Tgas >300 K)—Ice absorption bands are also seen
(H2O: 6 µm, CH4: 7,7 µm, NH3: 9 µm,CH3OH 9.7 µm, CO2: 15.2 µm,COMs: 5-7 µm)—PAH and ionized metal emission
lines are seen for evolved sources

NH310.705

10.735NH3NH3

10.77

10.74

11.63

11.68

NH3H2O

11.69

11.73

C2H2

H2O

NH312.40

C2H2

H2O

12.40

12.45

C2H2HCN

C2H2

H2O

C2H2
13.01

12.96

Fig.8 Gemini/TEXES spectra of a massive embedded
YSO, AFGL2136 IRS1 (R=85,000) [Indrilo+ 2020].

H2O

12.35

NH3

*See Boogert+ 98;van Dishoeck+ 96, 04;
Gonzaliz-Alfonso+ 98; Boonman+ 00, 03ab,Lahuis+ 00, 06; Dungee+ 18; Indrilo+ 20

NH3HCN
13.01

H2OC2H213.06

High-resolution MIR Spectroscopy of Massive YSOs
C2H2HCN
CO2ISO-SWS spectrum of Orion IRc2 (R=3500) [Boonman+ 03]

COMs ice
NH3 ice
CH3OH ice

CO2 ice

Ice absorption bands in MIR[Boogert+ 15]
Model
(20K)

H2O

CH4Model(100K)
Model(180K)

5.5
CO2 ice band at 15.2 µm [Boonman+ 03]

7
H2O n2 ro-vibrational line
[van Dishoeck 2004]

Obs.
(W33A)

7.4

7.8

CH4 n2/n4 ro-vibrational lines [Boogert+ 1998]

Summaryl GREX-PLUSは、これまでに無い高い感度で熱赤外線域のマゼラン雲の姿を描き出す
l AKARI/Spitzer/Herschelは大質量原始星の研究を銀河系外（マゼラン雲）へと広げた、GREX-PLUSはこれを小質量原始星に拡張し、銀河全体での幅広い質量範囲におよぶ星形成の様子を明らかにする
l マゼラン雲内に既に同定されている数百の大質量原始星の高分散分光により、原始星近傍の高温ガスの化学診断が可能になる
l 高分散分光については、5µm~のカバレッジがサイエンスの幅を大きく広げる
銀河のどこで星が生まれ、そこではどのような物質進化があり、それらは銀河の局所的な環境や大局的な構造とどう関連しているのか?
AGBサイエンスも重要!

重要!

ストもDiffuseダ

Spitzer, Herschel (SAGE, HERITAGE)

AKARI (LSLMC)

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