M 33 Dense Cloud Formation Global Star Formation
M 33高密度分子ガス観測にむけて Dense Cloud Formation & Global Star Formation in M 33 田村陽一 (東大・天文M 1, ALMA-J/NAOJ) 第 4回 銀河ショップ @ 北海道大学 October 18 -19, 2004
M 33 u R. A. 01 h 34 m u Decl. +30 o 40' u Type SA(s)cd u Distance 0. 85 Mpc u Inclination 56 o u Diameter 71'x 42' u Weak bulge • No SMBH? (Merritt et al. 2001) u Huge star forming region in outer disk • NGC 604, NGC 595. .
M 33 u Spitzer/IRAC (3. 6, 4. 5, 8 um) Polomski et al. 2004 u Hα Cheng et al. 1996
M 33 u NGC 604 HST/STSc. I
GMCs in M 33 u C. Wilson et al. w/ OVRO array • 系外銀河GMCの先駆的研究 u The BIMA All-Disk Survey (Engargiola et al. 2003) • 12 CO(1 -0) • 148 GMCs detected u Heyer et al. w/ FCRAO 14 m (2004) • Diffuseな成分も検出 • M(H 2) = 2. 6 x 108 Mo u MWに類似した性質 • Size, Mass, …
GMCs in M 33 NGC 604 NGC 505 Wilson & Scoville BIMA on FCRAO 14 m (Engargiola et al. 2003, Heyer et al. 2004)
The BIMA All-Disk Survey u u u (Engargiola et al. 2003) 148 GMCs detected Mmolecule =4. 5 x 107 Mo u u Engargiola et al. 2003, Deul & der Hulst 1987 2. 5 x 104 Mo 8 x 105 Mo Lifetime = 10 -20 Myr
GMC Mass Spectrum of M 33 u d. N/d. M=K(M/Mo)-α • α=2. 6 for M 33 u 3 x 104 -8 x 106 Mo u ~2000 GMCs u Index α • 1. 5 -1. 8 for MW (e. g. Solomon et al. 1987) • 1. 5(1. 9)± 0. 5 for LMC Engargiola et al. 2003 (Mizuno et al. 2001)
GMC Formation in M 33 u The BIMA Survey II (Rosolowsky et al. 2004) • BIMA C array (4" resolution ⇔ 20 pc) • 20 GMCs resolved • Size, Line width → Virial mass • Angular momentum u HI gasの凝集 u 理論より角運動量が小さい. • GMC形成理論に対する大きな制限 • 磁場によるブレーキ?
Star Formation in M 33 u Schmidt Law • ΣSFR ∝ (Σmolecule)n • n=0. 9± 0. 1 (Engargiola et al. 2003) • n=1. 36± 0. 08 (Heyer et al. 2004) u SFR = 0. 24 Mo yr-1 u 分子ガス消費時間 = 1. 9 x 108 yr • 比較的短い. • Mass spectrumと関連?
Star Formation in M 33 u GMC ⇔ HII region offset Δr • 典型的には~150 pc HII region GMC Δr Engargiola et al. 2003
Phase Transitions of Gases and Star Formation in Arms HI 175 pc GMC Dense gas / Core Star formation Wilson & Scoville 1991
Dense Molecular Gas Observation with Nobeyama Millimeter Array
Phase Transitions of Gases and Star Formation in Arms u HI filaments u GMCs u Dense Molecular Clouds • u 13 CO, GMC Dense gas / Core HCN, HCO+ …and Star formation • Hα / free-free emission u HI Main sequence stars • Subaru/Suprime-Cam Star formation
Phase Transitions of Gases and Star Formation in Arms u Clock • (OB) Stars u Dense gas / Core 江草ほか • なんてん ~ GMC phases u GMC すばる/Suprime-Cam • Arm - HII region offset u HI Yamaguchi et al. 2001 Star formation
Dense Gas Observation with NMA u Armにそって • GMCを複数個 • 似たmass/sizeのものを選択 u Gasの流れを追う • ガスの時間変化/進化/相転移 NMA Fo. V@110 GHz u 大規模星形成領域 • Pre- Star Formation • Ongoing Star Formation • Post- Star Formation
Dense Gas Observation with NMA GMC Dense Molecular Gas HII Region Spir al A rm Young Stars
How are GMCs in Extra-Galaxies seen with ALMA?
The Local Group Galaxies u ~0. 1" Resolution ⇔ 0. 4 pc ~ 1 x 105 AU @ M 33 (0. 85 Mpc) • MCの内部構造(clump, filament, . . )まで見える. • 系内GMC研究への歩み寄り(相補的) • [CI] line u GMC forming stage, Photo-Dissociation Region OMC w/ 1 m M 33 w/ ALMA Distance 390 pc 0. 85 Mpc Resolution 9' 0. 1 " (linear) 1 pc 0. 4 pc
Nearby Galaxies with D<20 Mpc u ~0. 1" Resolution ⇔ 10 pc @ Virgo (20 Mpc) • Fo. V of ALMA = 40" ⇔ 4 kpc • 前述のNMAやBIMAのM 33の観測をVirgo clusterで. u 数~10視野程度でdisk全体をカバーできる. u 1視野あたり~102 GMCs! • 銀河ごとのGMCの性質を統計的に議論することが可能. u Flocculent ⇔ Grand-design ? u GMC mass spectrum u Schmidt law
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