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A Submillimeter study of the Magellanic Clouds

A Submillimeter study of the Magellanic Clouds. Tetsuhiro Minamidani (Nagoya University) & NANTEN team ASTE team Mopra – ATNF team. Large Magellanic Cloud. Nearest galaxy ( ～ 50kpc) We can resolve individual GMCs. Face-on less contamination along the line of sight

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A Submillimeter study of the Magellanic Clouds

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  1. A Submillimeter studyofthe Magellanic Clouds Tetsuhiro Minamidani (Nagoya University) & NANTEN team ASTE team Mopra – ATNF team

  2. Large Magellanic Cloud • Nearest galaxy (～50kpc) • We can resolve individual GMCs. • Face-on • less contamination along the line of sight • Different environment from that of Our Galaxy • Low metallicity (e.g., Dufour 1984), • High gas to dust ratio (Koornneef 1982), • High FUV field • Active star formation • 30 Doradus ~ 39 O3 stars (Massey & Hunter 1999) • Current formation of young massive star clusters(populous clusters) • ~ 104 stars (e.g., Hodge 1961)

  3. Purpose of this work • Proto cluster condensation • Compact (<1pc), dense (104/cc) and warm (50K) • Derive density, temperature and kinematics ⇒ high resolution CO(J=3-2) • Envelope of molecular clouds • In low metallicity, intense UV environment • CO → C → C+ (PDR) ⇒ high resolution [CI] observation

  4. Outline • Results of CO(1-0) observations (NANTEN, SEST) • ASTE CO(3-2) observations • ASTE [CI] observations • Summary

  5. Molecular clouds in the LMC NANTEN 4m radio telescope 12CO(1-0) : 115GHz 259 CO clouds (Mvir > 104 Msun) Total molecular mass ~ 7×107 Msun • Reveal large scale distribution of GMCs in LMC • Complete sample of GMCs • Need higher resolution observations to find individual proto clustercondensations Total ~ 27,000 points Contours; from 1.2Kkm/s intervals 2.4Kkm/s

  6. Observations with SEST • Diameter: 15m • Line： 12CO(J=1-0) • Frequency: 115GHz • Beam size: 44”(115GHz) ⇒10pc@50kpc • Tsys: 450K(115GHz) • Vel. res.: 0.2 km/s (115GHz) • Observation: Aug., 2001 • Feb., 2002 (@La Silla, Chile)

  7. CO(3-2) Observations with ASTE Diameter： 10m Line： 12CO(J=3-2) Frequency：345GHz Beam size： 22”(345GHz) ⇒5pc@50kpc Observing grid: 30”, 20”, 15”, 10” Tsys： 300K (DSB) Intg. Time：30 – 240 sec. Vel. res. ： 0.44km/s (wide-band mode) Observation : Oct. 2004 (@Pampa la Bola, Chile)

  8. Proto cluster condensation ? • Cluster (Hunter et al. 2003) • size D = 1pc • M*tot = 3×102Msun • Star formation efficiency = 10% ↓ • Mgastot = 3×103Msun • dv = sqrt(Mgastot/(190×D/2)) = 5.62 km/s • M～105Msun, R～10pc, dv～7km/s (observed)

  9. From ASTE CO(3-2) obs. • Clump size ～ 10pc, • Clump mass ～ 105Msun • Substructure -> proto cluster condensation • I3-2/I1-0 - Hα flux correlation • From LVG analysis • Tkin > 120K, n(H2) ～ 104/cc (30Dor) • Tkin > 70K, n(H2) ～ 104/cc (N159W) • Clumps near the HII regions/clusters are heated

  10. [CI] line • Different environment from that of Our Galaxy • Low metallicity (e.g. Dufour 1984) • High gas to dust ratio (Koornneef 1982) • High FUV field ↓ • ＣＯ　→　Ｃ　→　Ｃ+ • [CII] : strongly depend to FUV field （Stacy et al. 1991, Mochizuki et al. 1994） • [CI]/CO : no significant dependence to FUV field （Bolatto et al. 2000）

  11. 30Dor -N159 region Bolatto et al. 2000 white: CII (55”) black: CO (33”) color : CI (250”) SEST CO(1-0) Johansson et al. 1998

  12. [CI] observations • ASTE telescope • Sept., 2003 • [CI] (3P1-3P0) 492.160651GHz • Beam size 15” • 3.6pc @ LMC(50kpc) • 4.3pc @ SMC(60kpc) • Observing grid • 30”, 20”, 15”, 7.5” • Velocity res. ～ 0.31km/s • Tsys～800 - K （DSB） • Intg. Time ～10min./on-position • Tr.m.s. ～ 0.5K

  13. From ASTE [CI] obs. • [CI] • Similar/weaker than the Galactic GMCs • 5～15km/s line width (larger than the Galactic GMCs) • N(C) : 0.8-3×1017cm-2（smaller than Orion） • N(C)/N(13CO) • No significant difference among 30Dor, N159W, N159S • Similar/larger than Orion

  14. Summary • CO(3-2) observations • Clump size is ～ 10pc, • Clump mass is ～ 105Msun ⇒larger than cluster’s size and mass ⇒substructure ⇒higher resolution observations ⇒compare to Spitzer data

  15. R(3-2)/(1-0) - Hα flux correlation • From LVG analysis • Tkin > 120K, n(H2) = 104±0.5/cc (30Dor) • Tkin > 70K, n(H2) ～ 104/cc (N159W) ⇒HII regions -> dust -> molecular gas ⇒compare to dust temperature • CO(3-2)/(1-0) sensitive to temperature • Determine density independently ⇒13CO

  16. [CI] Observations • [CI] • Weaker than the Galactic GMCs • 5～15km/s line width (larger than the Galactic GMCs) • N(C)/N(13CO) • N(C) : 0.8-3×1017cm-2（smaller than Orion） • No significant difference among 30Dor, N159W, N159S • Similar/larger than Orion ⇒ SMC ⇒ Detailed comparison LMC, SMC, Orion

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