A Submillimeter study of the Magellanic Clouds Tetsuhiro Minamidani (Nagoya University) & NANTEN team ASTE team Mopra – ATNF team

Large Magellanic Cloud Nearest galaxy ( ～ 50kpc) Nearest galaxy ( ～ 50kpc) We can resolve individual GMCs. We can resolve individual GMCs. Face-on Face-on less contamination along the line of sight less contamination along the line of sight Different environment from that of Our Galaxy Different environment from that of Our Galaxy Low metallicity (e.g., Dufour 1984), Low metallicity (e.g., Dufour 1984), High gas to dust ratio (Koornneef 1982), High gas to dust ratio (Koornneef 1982), High FUV field High FUV field Active star formation Active star formation 30 Doradus ~ 39 O3 stars (Massey & Hunter 1999) 30 Doradus ~ 39 O3 stars (Massey & Hunter 1999) Current formation of young massive star clusters (populous clusters) Current formation of young massive star clusters (populous clusters) ~ 10 4 stars (e.g., Hodge 1961) ~ 10 4 stars (e.g., Hodge 1961)

Purpose of this work Proto cluster condensation Proto cluster condensation Compact (<1pc), dense (10 4 /cc) and warm (50K) Compact (<1pc), dense (10 4 /cc) and warm (50K) Derive density, temperature and kinematics Derive density, temperature and kinematics ⇒ high resolution CO(J=3-2) Envelope of molecular clouds Envelope of molecular clouds In low metallicity, intense UV environment In low metallicity, intense UV environment CO → C → C + (PDR) CO → C → C + (PDR) ⇒ high resolution [CI] observation

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

Molecular clouds in the LMC NANTEN 4m radio telescope 12 CO(1-0) : 115GHz 259 CO clouds (Mvir > 10 4 M sun ) Total molecular mass ~ 7×10 7 M sun Total ~ 27,000 points Contours; from 1.2Kkm/s intervals 2.4Kkm/s Reveal large scale distribution of GMCs in LMC Reveal large scale distribution of GMCs in LMC Complete sample of GMCs Complete sample of GMCs Need higher resolution observations to find individual proto cluster condensations Need higher resolution observations to find individual proto cluster condensations

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

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

Proto cluster condensation ? Cluster (Hunter et al. 2003) Cluster (Hunter et al. 2003) size D = 1pc size D = 1pc M * tot = 3×10 2 M sun M * tot = 3×10 2 M sun Star formation efficiency = 10% Star formation efficiency = 10%↓ M gas tot = 3×10 3 M sun M gas tot = 3×10 3 M sun dv = sqrt(M gas tot /(190×D/2)) = 5.62 km/s dv = sqrt(M gas tot /(190×D/2)) = 5.62 km/s M ～ 10 5 M sun, R ～ 10pc, dv ～ 7km/s (observed) M ～ 10 5 M sun, R ～ 10pc, dv ～ 7km/s (observed)

From ASTE CO(3-2) obs. Clump size ～ 10pc, Clump size ～ 10pc, Clump mass ～ 10 5 M sun Clump mass ～ 10 5 M sun Substructure -> proto cluster condensation Substructure -> proto cluster condensation I 3-2 /I Hα flux correlation I 3-2 /I Hα flux correlation From LVG analysis From LVG analysis Tkin > 120K, n(H 2 ) ～ 10 4 /cc (30Dor) Tkin > 120K, n(H 2 ) ～ 10 4 /cc (30Dor) Tkin > 70K, n(H 2 ) ～ 10 4 /cc (N159W) Tkin > 70K, n(H 2 ) ～ 10 4 /cc (N159W) Clumps near the HII regions/clusters are heated Clumps near the HII regions/clusters are heated

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

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

ASTE telescope ASTE telescope Sept., 2003 Sept., 2003 [CI] ( 3 P P 0 ) GHz [CI] ( 3 P P 0 ) GHz Beam size 15 ” Beam size 15 ” LMC(50kpc) LMC(50kpc) SMC(60kpc) SMC(60kpc) Observing grid Observing grid 30 ”, 20 ”, 15 ”, 7.5 ” 30 ”, 20 ”, 15 ”, 7.5 ” Velocity res. ～ 0.31km/s Velocity res. ～ 0.31km/s Tsys ～ K （ DSB ） Tsys ～ K （ DSB ） Intg. Time ～ 10min./on-position Intg. Time ～ 10min./on-position Tr.m.s. ～ 0.5K Tr.m.s. ～ 0.5K [CI] observations

From ASTE [CI] obs. [CI] [CI] Similar/weaker than the Galactic GMCs Similar/weaker than the Galactic GMCs 5 ～ 15km/s line width (larger than the Galactic GMCs) 5 ～ 15km/s line width (larger than the Galactic GMCs) N(C) : 0.8-3×10 17 cm -2 （ smaller than Orion ） N(C) : 0.8-3×10 17 cm -2 （ smaller than Orion ） N(C)/N( 13 CO) N(C)/N( 13 CO) No significant difference among 30Dor, N159W, N159S No significant difference among 30Dor, N159W, N159S Similar/larger than Orion Similar/larger than Orion

Summary CO(3-2) observations CO(3-2) observations Clump size is ～ 10pc, Clump size is ～ 10pc, Clump mass is ～ 10 5 M sun Clump mass is ～ 10 5 M sun ⇒ larger than cluster’s size and mass ⇒ substructure ⇒ higher resolution observations ⇒ compare to Spitzer data

R(3-2)/(1-0) - H α flux correlation R(3-2)/(1-0) - H α flux correlation From LVG analysis From LVG analysis Tkin > 120K, n(H 2 ) = 10 4±0.5 /cc (30Dor) Tkin > 120K, n(H 2 ) = 10 4±0.5 /cc (30Dor) Tkin > 70K, n(H 2 ) ～ 10 4 /cc (N159W) Tkin > 70K, n(H 2 ) ～ 10 4 /cc (N159W) ⇒ HII regions -> dust -> molecular gas ⇒ compare to dust temperature CO(3-2)/(1-0) sensitive to temperature CO(3-2)/(1-0) sensitive to temperature Determine density independently Determine density independently ⇒ 13 CO

[CI] Observations [CI] Observations [CI] [CI] Weaker than the Galactic GMCs Weaker than the Galactic GMCs 5 ～ 15km/s line width (larger than the Galactic GMCs) 5 ～ 15km/s line width (larger than the Galactic GMCs) N(C)/N( 13 CO) N(C)/N( 13 CO) N(C) : 0.8-3×10 17 cm -2 （ smaller than Orion ） N(C) : 0.8-3×10 17 cm -2 （ smaller than Orion ） No significant difference among 30Dor, N159W, N159S No significant difference among 30Dor, N159W, N159S Similar/larger than Orion Similar/larger than Orion ⇒ SMC ⇒ Detailed comparison LMC, SMC, Orion