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SMA Observations of Magnetic Fields in Low Mass Star Forming Regions

SMA Observations of Magnetic Fields in Low Mass Star Forming Regions. Ramprasad Rao (ASIAA), Josep Miquel Girart (IEEC-CSIC), and the SMA Polarimetry Team. And what these observations tell us about B. B-Field Ambipolar Diffusion Regulated star formation. Crutcher 2006.

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SMA Observations of Magnetic Fields in Low Mass Star Forming Regions

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  1. SMA Observations of Magnetic Fields in Low Mass Star Forming Regions Ramprasad Rao (ASIAA), Josep Miquel Girart (IEEC-CSIC), and the SMA Polarimetry Team And what these observations tell us about B.

  2. B-Field Ambipolar Diffusion Regulated star formation Crutcher 2006

  3. Simulations of polarized dust emission Goncalves et al. 2005

  4. R=0.02 pc ~ 4000 AU Bethell et al. 2007

  5. Tool of Choice: Submm/mm Polarimetry • Advantages of emission polarimetry • emission is optically thin • no contamination from scattering, absorption etc. • Single dish measurements (CSO/Hertz/SHARP, JCMT/SCUBA) • good sensitivity to large scale structure • Dust emission strong at submm • Resolution is low ~10” • Highly sensitive interferometer array observations are needed. OVRO and BIMA earlier, currently SMA and CARMA, future with ALMA • BUT, cannot directly give strength of B

  6. Polarization Targets • Low Mass: NGC 1333, IRAS 16293 A/B, HL Tau, L1551IRS5, VLA1623, Barnard 1c, Serpens Molecular cloud etc. • High mass: G5.89, G30.79 FIR10, IRAS20126, G31.41, Orion-KL etc. • SMA High Mass Legacy project: See Talk by Zhang Q. PI

  7. NGC 1333Cloud Sandell & Knee 2001 SCUBA 850 m

  8. NGC 1333 IRAS 4A C-F method gives B~ 5 mG; B fields likely to be dominant over turbulence B Field Girart et al. 2006

  9. However, what is missing is the connection to large scale fields …!!!

  10. Large scale SHARP Matthews+ 2009; SCUPOL combination of both small scale and large scale structure is needed SMA Attard+ 2009; Slide courtesy Giles Novak

  11. NGC 1333 IRAS 4B SMA SCUPOL

  12. NGC 1333 IRAS 2A SMA SCUPOL IRAS2

  13. Ophiuchus Bolocam 1.1mm 31” resolution Young et al. 2006

  14. IRAS 16293 Outflow Line joining Aa, Ab B-field

  15. IRAS16293: SCUBA E Field Matthews et al. (2009)

  16. SCUPOL VLA1623 SMA JCMT Holland et al. 1996

  17. Serpens Molecular Cloud Enoch et al. (2011) Bolocam 1.1mm Spitzer 24 micron Distance ~ 415 pc

  18. Serpens In prep.

  19. Taurus: Class I sources HL Tau L1551 IRS 5 Pmax~less than 1+/-0.5% at the center Tamura et al. 1995 JCMT

  20. Low Mass Stars: Summary • Some Class 0 sources show resolved and ordered magnetic fields e.g. NGC 1333 IRAS 4A • Other Class 0 sources show none or disordered e.g. VLA 1623 • Class I sources show weak or undetected polarization

  21. Conclusions Magnetic fields appear to be dominant in quite a few of the objects Sensitivity is still an issue - improvements made at the SMA ALMA will be great when it comes online for polarization observations - but need short spacing data "If the sun didn't have a magnetic field, then it would be as boring a star as most astronomers think it is.” – quote attributed to R. Leighton “Magnetic fields are to astrophysicists what sex is to psychoanalysts.” - H. C. van de Hulst Thank You!!

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