A Submillimeter study of the Magellanic Clouds Tetsuhiro
A Submillimeter study of the Magellanic Clouds Tetsuhiro Minamidani (Nagoya University) & NANTEN team ASTE team Mopra – ATNF team
Large Magellanic Cloud n Nearest galaxy (~ 50 kpc) n n Face-on n n Low metallicity (e. g. , Dufour 1984), High gas to dust ratio (Koornneef 1982), High FUV field Active star formation n n less contamination along the line of sight Different environment from that of Our Galaxy n n We can resolve individual GMCs. 30 Doradus ~ 39 O 3 stars (Massey & Hunter 1999) Current formation of young massive star clusters (populous clusters) n ~ 104 stars (e. g. , Hodge 1961)
Purpose of this work n Proto cluster condensation Compact (<1 pc), dense (104/cc) and warm (50 K) n Derive density, temperature and kinematics ⇒ high resolution CO(J=3 -2) n n Envelope of molecular clouds In low metallicity, intense UV environment n CO → C+ (PDR) ⇒ high resolution [CI] observation n
Outline Results of CO(1 -0) observations (NANTEN, SEST) n ASTE CO(3 -2) observations n ASTE [CI] observations n Summary n
Molecular clouds in the LMC NANTEN 4 m radio telescope 12 CO(1 -0) : 115 GHz n 259 CO clouds (Mvir > 104 Msun) Reveal large scale distribution of GMCs in LMC n n Complete sample of GMCs Total molecular mass ~ 7× 107 Msun Need higher resolution observations to find individual proto cluster condensations Total ~ 27, 000 points Contours; from 1. 2 Kkm/s intervals 2. 4 Kkm/s
Observations with SEST Diameter: 15 m 12 CO(J=1 -0) Line: Frequency: 115 GHz Beam size: 44”(115 GHz) ⇒ 10 pc@50 kpc Tsys: 450 K(115 GHz) Vel. res. : 0. 2 km/s (115 GHz) Observation: Aug. , 2001 Feb. , 2002 (@La Silla, Chile)
CO(3 -2) Observations with ASTE Diameter: 10 m 12 CO(J=3 -2) Line: Frequency: 345 GHz Beam size: 22”(345 GHz) ⇒ 5 pc@50 kpc Observing grid: 30”, 20”, 15”, 10” Tsys: 300 K (DSB) Intg. Time: 30 – 240 sec. Vel. res. : 0. 44 km/s (wide-band mode) Observation : Oct. 2004 (@Pampa la Bola, Chile)
Proto cluster condensation ? n Cluster (Hunter et al. 2003) size D = 1 pc n M*tot = 3× 102 Msun n Star formation efficiency = 10% ↓ n Mgastot = 3× 103 Msun n dv = sqrt(Mgastot/(190×D/2)) = 5. 62 km/s n n M~ 105 Msun, R~ 10 pc, dv~ 7 km/s (observed)
From ASTE CO(3 -2) obs. Clump size ~ 10 pc, n Clump mass ~ 105 Msun n n Substructure -> proto cluster condensation n I 3 -2/I 1 -0 - Hα flux correlation n From LVG analysis Tkin > 120 K, n(H 2) ~ 104/cc (30 Dor) n Tkin > 70 K, n(H 2) ~ 104/cc (N 159 W) n Clumps near the HII regions/clusters are heated n
[CI] line n Different environment from that of Our Galaxy n n n Low metallicity (e. g. Dufour 1984) High gas to dust ratio (Koornneef 1982) High FUV field ↓ CO → C+ [CII] : strongly depend to FUV field (Stacy et al. 1991, Mochizuki et al. 1994) n [CI]/CO : no significant dependence to FUV field (Bolatto et al. 2000)
30 Dor -N 159 region SEST CO(1 -0) Johansson et al. 1998 Bolatto et al. 2000 white: CII (55”) black: CO (33”) color : CI (250”)
[CI] observationsn ASTE telescope n n n Sept. , 2003 [CI] (3 P 1 -3 P 0) 492. 160651 GHz Beam size 15” n n n n 3. 6 pc @ LMC(50 kpc) 4. 3 pc @ SMC(60 kpc) Observing grid n 30”, 20”, 15”, 7. 5” Velocity res. ~ 0. 31 km/s Tsys~ 800 - K (DSB) Intg. Time ~ 10 min. /on-position Tr. m. s. ~ 0. 5 K
From ASTE [CI] obs. n [CI] Similar/weaker than the Galactic GMCs n 5~ 15 km/s line width (larger than the Galactic GMCs) n N(C) : 0. 8 -3× 1017 cm-2 (smaller than Orion) n n N(C)/N(13 CO) No significant difference among 30 Dor, N 159 W, N 159 S n Similar/larger than Orion n
Summary n CO(3 -2) observations Clump size is ~ 10 pc, n Clump mass is ~ 105 Msun ⇒larger than cluster’s size and mass ⇒substructure ⇒higher resolution observations ⇒compare to Spitzer data n
R(3 -2)/(1 -0) - Hα flux correlation n From LVG analysis n n Tkin > 120 K, n(H 2) = 104± 0. 5/cc (30 Dor) n Tkin > 70 K, n(H 2) ~ 104/cc (N 159 W) ⇒HII regions -> dust -> molecular gas ⇒compare to dust temperature n CO(3 -2)/(1 -0) sensitive to temperature n Determine density independently ⇒ 13 CO
n [CI] Observations n [CI] n Weaker than the Galactic GMCs n 5~ 15 km/s line width (larger than the Galactic GMCs) n N(C)/N(13 CO) n N(C) : 0. 8 -3× 1017 cm-2 (smaller than Orion) n No significant difference among 30 Dor, N 159 W, N 159 S n Similar/larger than Orion ⇒ SMC ⇒ Detailed comparison LMC, SMC, Orion
- Slides: 16