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Sub-mm/mm astrophysics: How to probe molecular gas Yasuo Fukui Nagoya University Summer School

Sub-mm/mm astrophysics: How to probe molecular gas Yasuo Fukui Nagoya University Summer School The Gaseous Universe Oxford, 21-23 July 2010. Lecture 2 Sub-mm diagnostics; density and temperature. Sub-mm/mm astrophysics: How to probe molecular gas.

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Sub-mm/mm astrophysics: How to probe molecular gas Yasuo Fukui Nagoya University Summer School

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  1. Sub-mm/mm astrophysics: How to probe molecular gas Yasuo Fukui Nagoya University Summer School The Gaseous Universe Oxford, 21-23 July 2010

  2. Lecture 2Sub-mm diagnostics; density and temperature Sub-mm/mm astrophysics: How to probe molecular gas

  3. Sub-mm diagnostics; density and temperature In lecture 1, we have learned the fundamentals of molecular data at sub-mm and mm wavelengths. Now we apply the method to real data taken with best telescopes in order to derive physical parameters of the molecular gas. By comparing different J transitions we can determine density and temperature by LVG approximation

  4. Radiative transfer (εν(x): Emission coefficient, κν(x): Absorption coefficient) Optical depth:

  5. Absorption coefficients φ(ν): line profile function - When φ(ν) takes a Gaussian function.

  6. Rotational excitation of a diatomic-molecule • Eigenvalue of energy (Quantum mechanics) • Rotational quantum number, J (J = 0,1,2,3,…) • ΔJ = ±1 • A coefficient

  7. Excitation temperature & Optical depth • 13CO J=1-0 (LTE assumption) • Radiation (Observed) Temperature, TR* (*Back ground of spectral line is removed) • Since τ12CO(optical depth of 12CO J=1-0) ≥ 1 • Then, derive τ13CO (optical depth of 13CO J=1-0)

  8. Column density • Partition function, Q

  9. LVG approximation LVG (Large Velocity Gradient) (Castor 1970; Goldreich & Kwan 1974; Scoville & Solomon 1974 • Simple molecular cloud model • Uniform Tk and n(H2) • Uniform velocity gradient Photon escape probability, β • Input parameters: Tk, n(H2), [CO]/[H2] abundance ratio X(CO), velocity gradient dv/dr Molecular cloud Velocity • Spherical • Slab Tk, n(H2)

  10. Part I N159 and other GMCs in the LMC

  11. The Large Magellanic Cloud Magellanic Clouds • D=50 kpc (one of the nearest) • Different environment from the MW. • High gas-dust ratio • Low metallicity • Active star formation • Massive star formation • Young populous clusters The Small Magellanic Cloud

  12. Excitation 2 • Hydrogen molecules are not observable in radio. Too high energy levels. Only in absorption. • Carbon monoxide CO and others can be observed rotational energy levels, high excitation vibration. cf. electronic, spin-spin interaction • Sub-mm transitions generally higher excited states ratio between J and J’ gives density/tempearture.

  13. 100 80 60 （K km/s） 40 20 0 N159 (Type III) N206D (Type II) GMC225 (Type I) 12CO（J=3-2） 12CO（J=1-0） Minamidani et al. 2008

  14. NN159 CO 3-2/1-0 vs. Ha

  15. 30Dor No.1 15-40K, 103cm-3 (cool, diffuse) ＞ 50K, 103-5cm-3 (warm, dense) ＞ 30K, 103cm-3 (warm. diffuse) GMC225 No.1 N206 No.1 XCO = 3×10-6； solid：R3-2/1-0,clump；broken：R12/13

  16. High temp. High density Low density 低温・低密度

  17. NANTEN2 CO J=4-3 observationsMizuno et al. 2010 N159 region in the LMC CO(J=4-3) CO(J=1-0) CO(J=3-2) N159E N159W N159S Mopra ASTE NANTEN2 Spitzer(8, 24mm) (Meixner et al.2006) +NANTEN2 CO (4-3)

  18. Results：N159W 1s level • Temperature72+3-9 (K) • Density4.0+0.0-0.0×103(cm-3)

  19. Results：N159E • Temperature79+13-12 (K) • Density4.0+1.0-0.0×103(cm-3)

  20. Results：N159S • Temperature31+8-9 (K) • Density1.6+0.4-0.3×103(cm-3)

  21. Comparison with the observed intensities N159W, E:12CO J=1-0, 2-1 are weaker than that expected from LVG

  22. Physical conditions in the clumps • N159W, N159E：２ components • N159S：１ component 12CO J=4-3, J=3-2 Hot Dense ~ 80 K 13CO 12CO J=1-0 Cold ~ 30 K 12CO J=4-3, J=3-2 13CO Cold ~ 30 K 12CO J=1-0

  23. Contours：12CO(J=4-3) Image：optical B, V, Ha, O III (ESO) Star formation

  24. Molecular clouds and star formation N159W ＊massive star formation ＊Ionized gas 　　　　　＋ ＊pre star forming region N159E ＊Massive star formation＊extended ionized gas N159S ＊No massive star formation ＊cold Cold molecular gas High excited region Ionized region

  25. Sky Condition at Atacama –Atmospheric Tau vs PWV- 13CO 12CO Winter season Winter season Summer season Summer season Sky condition at 100GHz in summer is not different from that in winter

  26. NANTEN2

  27. NANTEN & NANTEN2 @Las Campanas, alt.2400m @Atacama, alt.4800m

  28. Part II Westerlund 2, case of super-star cluster

  29. Super star cluster in the MW • O stars are rare in the MW • It is important to study nearby young and rich cluster but, only five super star clusters in the MW Arches Cluster Quintuplet Cluster Central Cluster Genzel et al. 2003 1.2[pc] 0.6[pc] Figer et al. 1999 0.4[pc] Genzel et al. 2003 Figer et al. 1999

  30. Westerlund 2(Wd2) Spitzer IRAC 3.6, 4.5, 5.8, 8.0 m HESS J1023-575 • Total mass of star:4500 Msun • (Rauw et al. 2007) • Age ：2-3 Myr • (Piatti et al. 1998) • O type star：12 • (Rauw et al. 2007) • Wolf-Rayet (WRs) star ：2 • 　 (Rauw et al. 2007) • Distance:2.8 kpc(Ascenso et al.2007) • 4.3 ± 1.4 kpc(Furukawa et al.2009) • 8.3 ± 1.6 kpc (Rauw et al. 2007) HII region RCW 49 • HII region associated with • the cluster　(Churchwell et al. 2004) • YSOs: 300 (Whitney et al. 2004)

  31. Distribution of line intensity ratio image: integrated intensity, cont.:CO(2-1) Red cross：Wd2 Ratio 12CO2-1/12CO1-0 Ratio 12CO2-1/13CO2-1 15 2.0 1.5 10 1.0 5 0.5 0 0 Ratio is high near the cluster

  32. line：12CO2-1/12CO1-0 wiggle line: 12CO2-1/13CO2-1 LVG Analysis Gray ：error range15% High Temp. Low Temp. Estimation of temperature and density by using the LVG analysis including 13CO(J=2-1)

  33. Temperature distribution of the molecular clouds Image: Temperature, cont.:12CO(2-1) red cross：Wd2 4 km/s Cloud 16 km/s Cloud Suggesting gas is heated by the raditation from the cluster.

  34. Temperature with distance from Wd2 星団から離れるにつれて 減少している。 星団周辺で高温 高温 →分子雲全体がHII領域に付随している Molecular clouds are associated with Wd2 and RCW 49 Ohama, Furukawa et al. 2010

  35. Part III Galactic centre loops Torii et al. 2010 and others

  36. The Galactic Centre NANTEN CO J=1-0 • Galactic centre has strong gravity • Strong differential rotation amplifies the magnetic field • Molecular gas is nearly neutral, but frozen-in is a good description. Ionization degree 10-7 from HCO+ CMZ

  37. 200 pc 300 pc Molecular loops 1 & 2 （Fukui et al. 2006, Torii et al. 2010a） NANEN CO J=1-0 ・ Two loop like structures ・ foot points with broad velocity dispersion (~40km/s) ・Total M ~106 Msun

  38. Parker Instability (Parker 1966) Magnetic field • Parker instability drives the neutral gas • Magnetic flotation in the sun takes place 12 orders of magnitude greater scale • Key parameters are scale height H and Alfvén speed VA • Time scale of the process is H/VA, 1-10 Myrs Gravity Gas particle

  39. 2D MHD calculations (Matsumoto et al. 1988) • Gas accumulation at the two foot points, shock heating • Any part of the loop is also being shocked, high temperature

  40. 12CO(J=3-2) observations ASTE CO(J=3-2) -180 - -40 km/s NANTEN CO J= 1-0 Torii et al. 2010b

  41. 12CO(J=3-2)/12CO(J=1-0) ratio：　R3-2/1-0 P-V diagram Color：R3-2/1-0, Contours：ASTE CO(J=3-2)　 High R3-2/1-0 inside the U shape

  42. Broad emission　Spectra LVG analysis カラー：R3-2/1-0, コントア：ASTE CO(J=3-2)　 空間分布図 Ａ • 12CO(J=1-0, 3-2, 4-3, 7-6), 13CO(J=1-0), C18O(J=1-0) • Take 10 km/s average intensities • [12CO]/[13CO] 〜 53 　 (Riquelme 2010) • [12CO]/[C18O] 〜 250 (i.e. Wilson & Matteucci 1992) • [12CO]/[H2] = 1×10-4 • dv/dr= 9.0 km/s/pc • Chi-square minimization B C

  43. LVG analysis – Results – Typically T 〜30-50 K, n〜103 /cm3 Broad emission : > 100 K Magnetic reconnection may offers a possible candidate for the hot and broad gas component.

  44. Degree of excitationR3-2/2-1 Distributions in the loops 1 and 2 12CO(J=3-2)/12CO(J=2-1)

  45. R3-2/2-1 Histogram All • Loops 1 and 2: peak at 0.42 • Disk components: peak at 0.24-0.3 Loops 1 & 2 Disk (-40 - -20 km s-1) Disk (-20 - 0 km s-1) Disk (0 - 20 km s-1)

  46. R3-2/2-1 and physical conditions >103cm-3 , >70 K 0.7

  47. LVG analysis T: 10 – 50 K, >100 K n(H2): ~ 103.0 cm-3 R3-2/2-1>0.7 indicate T of >70 K R3-2/2-1>0.7 R3-2/2-1>0.7

  48. appendix

  49. Derivation of physical parameters • Rayleigh-Jeans approximation • Column density: • τ << 1 case

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