Hiroshi Imai (Joint Institute for VLBI in Europe) Anuj P. Sarma (Eastern Kentucky University)

1. European Workshop on Astronomical MoleculesZwolle, the Netherlands in 19 February 2004The Kinematics, Physical Condition and Magnetic Field of the W3 IRS5 Region Hiroshi Imai (Joint Institute for VLBI in Europe) Anuj P. Sarma (Eastern Kentucky University)

2. European Workshop on Astronomical MoleculesZwolle, the Netherlands in 19 February 2004The Kinematics, Physical Condition and Magnetic Field of the W3 IRS5 Region Hiroshi Imai (Kagoshima University, Japan) Anuj P. Sarma (Eastern Kentucky University)

3. Diagnostics of early phase of star formation with water masers • About W3 IRS5 • Water maser kinematics: • Finding driving sources of the outflows • Magnetic field • Zeeman splitting (B//) • Linear polarization (B⊥) • Physical condition • Turbulence in the outflows/ambient gas • Conclusions • How has W3 IRS5 been understood?

4. About W3 IRS5: bright sum-mm source • Bight Far-IR and sub-mm source in W3 Main • Earliest phase of star formation Cited from Ladd et al. (1993)

5. About W3 IRS5: a molecular cloud core W3 Main • M~1400 Msun (Hayashi et al. 1989) C18O (contour) and 21 cm continuum emission in W3 Main (Tieftrunk et al. 1995; Colley 1980)

6. About W3 IRS5: polarimetry • Magnetic field in W3 Main (Roberts et al. 1993; Greaves et al. 1994, 2003) • Spatial gradient in NE--SW direction • Weakening at the location of W3 IRS5 A molecular outflow (Mitchell et al. 1993)

7. About W3 IRS5: a high-mass star cluster Water masers and 15-GHz continuum emission sources (Claussen et al. 1994) 6000 AU at 1.8 kpc • Hyper compact HII regions? • Or blobs of ionized gas in one outflow? • Where is the high-mass YSOs (outflow driving sources)? • How old is this star-forming region?

8. VLBA observations of the W3 IRS5 water masers • Observations • Proper motion measurement March 1997, October 1997 and January 1998 • Polarimetry (Linear polarization, with the VLA) November 1998 • Polarimetry (Zeeman effect measurement) January 2000

9. VLBA observations of the W3 IRS5 water masers • Publications • Imai et al. 2000, ApJ 538, 751 • Sarma et al. 2001, ApJ 554, L217 • Imai, Deguchi & Sasao 2002, ApJ 567, 971 • Watson, Sarma & Singleton 2002, ApJ 570, L37 • Imai et al. 2003, ApJ 595, 285

10. Water maser kinematics(Imai et al. 2000) • Distance to W3 IRS5: ~1.8 kpc • c.f. .... • 2.3 kpc (kinematic distance)(Georgelin & Georgelin 1972) • 2.2 kpc (Cas OB6, spectroscopic) (Humphreys 1978) • 2.4 kpc (IC1805, spectroscopic) (Guetter et al. 1989) • 1.8 kpc (IC1795, spectroscopic) (Ogura & Ishida 1976) • Wait for annual parallax measurements. (W3 OH, Hachisuka et al. 2004)

11. Water maser kinematics(Imai et al. 2000) • Two distinct outflows from sources a and d1/d2 >>> almost same evolutionary stage (Δτ≦ 105 years) • Outflow velocities: ~30 km/s • Accelerated up to ~60 km/s

12. Water maser kinematics(Imai et al. 2000) • Improved partially by continuum proper motions (Wilson et al. 2003) • Fixed relative positions between sources b and d1/d2>>> at least 2 early B-stars • Proper motions of sources aand fwith velocities ~130 km/s • Sources c and e disappeared.

13. Water maser polarimetry:Tracing magnetic field of the interior of a molecular cloud core • Magnetic field on a tiny scale (< 1000 AU) • Regions very close to outflow origins and protostars • Sites of the earliest phase of star formation • Really tracing magnetic field of molecular core? • Relation to the magnetic field on a larger scale • Local effects in maser phenomenon?

14. Water maser polarimetry (Sarma et al. 2001, 2002) • Velocity resolution better than 0.1 km/s is necessary. • Similar values of magnetic field strengths in four maser features: B//~ -30 mG

15. Proper motions v.s. Electric Vector PAs (Imai et al. 2003)

16. The magnetic field model in W3 IRS5 0.5 pc at 1.8 kpc Uniform B vector in the maser region B⊥ PA in the maser region: ~75 deg. B// inclination w.r.t. LOS 45--60 deg.

17. The magnetic field model in W3 IRS5 0.5 pc at 1.8 kpc An hourglass model (Roberts et al. 1993) Pinch center at the east of the maser region (Sub-mm emission peak, Ladd et al. 1993) Pinch ratio: A:B~1:7

18. Magnetic field between on large and small scales • Empirical B-n relation of magnetic field • (Clutcher 1999) • ~25μG >>> ~1 mG pinch ratio ~7 >>> Enhanced by a factor ~50 • Enhanced by a factor ~20 in maser clumps Bcritical =(8πρmaserv2maser)1/2~ 250 mG < Bobserved >>> The magnetic field cannot control the outflows.

19. Microstructures in water masers(Imai et al. 2002) How to create such structures?

20. Two-point correlation functions(Imai et al. 2002) Fractal fashion in the outflow and maser gas clumps. (c.f. Gwinn 1994; Strelniski et al. 1999; A.Richards’s talk) Flatter slop created more energetic flow and crating more intense maser emission.

21. Velocity difference in maser clumps(Imai et al. 2002) Kolmogorov-type turbulence in a maser cloud Common among water maser sources Turbulence enhanced only on the outflow scale

22. Improved from Imai et al. (2000) How has W3 IRS5 been understood?

23. Conclusions • Water maser kinematics for successfully finding driving sources in a cluster of newly-formed massive-stars. • Cluster formation on a very short time scale (105 yr) • Synchrotron emission blobs in stellar winds • Water maser polarimetry for successfully elucidating 3D magnetic field at the center of a molecular cloud core. • Magnetically supercritical collapse of a core • Outflows dominated by stellar winds • Common turbulence at interior and exterior of maser clumps • Turbulence is excited only at exterior of maser clumps by outflows/stellar winds.