1. Mapping Magnetic Field Structure in Star-forming Regions 賴詩萍 Oct 4, 2006, NTHU Phys Colloquium

3. 康德 - 拉普拉斯 星雲假說 康德 (1755 年 ) - 原始星雲是由大小不等的 固體微粒組成的﹐ “ 天體在吸引最強的地方 開始形成 ” ﹐萬有引力使得微粒相互接近。 拉普拉斯 (1796 年 ) - 形成太陽系的雲是一 團巨大的﹑灼熱的﹑轉動著的氣體﹐大致呈球 狀。由於冷卻﹐星雲逐漸收縮, 星雲的中心 部分凝聚成太陽 。

4. Star formation standard model Shu et al. 1987 Shu et al. (1987)

5. Star formation standard model P. Andre

6. Starless Cores – Barnard 68

7. Simplest Star Formation Theory Thermal pressure support Thermal pressure support - Jeans Mass (1928) Gravitation Thermal Pressure

8. Why B is important in star formation? Regulating star formation efficiency Observed star formation efficiency is low Theoritical 200 M  /year >> Observed 3 M  /year B provides support in Static fields MHD waves (turbulence) Facilitating gravitational collapse Angular momentum problem – magnetic braking Magnetic flux problem - ambipolar diffusion

9. Magnetic support theories MHD simulations MHD simulations (Ostriker, Gammie, & Stone 1999) Morphology Evolution large -> random morphology

10. How to measure B? Zeeman Effect – Too Difficult!! Polarization of Dust Emission: P  B p Polarized Molecular Line Emission (the Goldreich-Kylafis Effect): P  B p or P  B p B V

11. Polarization Observations with Berkeley-Illinois-Maryland Array (BIMA)

12. Dust Polarization observations with BIMA

13. Magnetic Field Morphology Magnetic Field Morphology – W51 e1/e2 JCMT   14” at 850  m BIMA   2” at 1.3 mm Lai et al. (2001)Chrysostomou et al. (2002)

14. NGC 2024 Matthews et al. (2002) JCMT   14” at 850  m BIMA   2” at 1.3 mm Lai et al. (2002)

15. DR21(OH) – JCMT vs. BIMA (B map) Lai et al. (2003)

16. NGC1333 IRAS4A

18. Twisted hour- glass geometry NGC1333 IRAS4A

19. BIMA   2” at 1.3 mm SMA   1” at 850  m Lai (2002)Girart, Rao, Marrone (2006)

20. Physical quantities Dispersion of Polarization Angle () Dispersion of Polarization Angle (  ) 1. Field Strengths (the Chandrasekhar-Fermi Method) 2. Mass-to-magnetic-flux Ratios 3. Turbulent-to-magnetic-energy Ratios

21. Dispersion of Polarization Angle () Dispersion of Polarization Angle (  ) ⇒ Field Strengths in the plane of sky Uniform fields perturbed by MHD turbulence - Incompressible fluid -  invariant Small perturbation - Isotropic turbulence - Chandrasekhar-Fermi Method Ostriker, Stone, & Gammie 2001

22. Results B p ~ 0.8 – 3.5 mG Φ M/ Φ B,p ~ 0.1 – 4.9 critical mass-to-flux ratio   turb ~ 0.03 – 0.4 B p, M/ Φ B,p,  turb  ⇒ B p, M/ Φ B,p,  turb

23. Future Work – More observations!! Current/Future instruments SMA (the only working interferometer for now) CARMA = BIMA + OVRO (?) ALMA!! (wait at least 7 years) 3D Magnetic Field Structure Zeeman measurements High density (10 6 cm -3 ) - CN Young Cores – CCS Line polarization

24. ALMA in 7 years

25. 廣告時間 “Star and Planet formation” Journal Club 時間 : 隔週週二中午 12:10-1:00 pm 地點 : 502A 目的 輪流報告最新的研究結果 培養學生對這個研究主題的興趣 參與老師 : 江瑛貴, 陳惠茹, 呂聖元, 賴詩萍