1. Tracking the Magellanic Stream(s): From Birthplace out to100° David L. Nidever University of Virginia Collaborators: Steven R. Majewski and W. Butler Burton (NRAO)

2. Previous Work Observations HI Magellanic Stream Putman et al. 1998, 2003 Stanimirović et al. 2002 Brüns et al. 2005 HI LMC Staveley-Smith et al. 2003 Kim et al. 2003 HI SMC & Bridge Staveley-Smith et al. 1995 Stanimirović et al. 1999, 2000, 2004 CO Yamaguchi et a. 2001 Hα Weiner & Williams 1996 Putman et al. 2003 Simulations/Theory Tidal Models Lin & Lynden-Bell 1977, 1982 Murai & Fujimoto 1980 Gardiner et al. 1994, 1996, 1999 Connors et al. 2004, 2005 Yoshizawa & Noguchi 2003 Bekki et al. 2005 Ram Pressure Moore & Davis 1994 Mastropietro et al. 2004

3. Background Discovery Papers A long stream of HI gas trailing the Magellanic Clouds. Large velocity gradient (Wannier & Wrixon 1972, Mathewson et al. 1974)

4. Background Early Models Tidal models reproduce general features of Stream. (Lin & Lynden-Bell 1977, 1982, Murai & Fujimoto 1980) Murai & Fujimoto 1980 600 particles Lin & Lynden-Bell 1977 200 particles Moore & Davis 1994 Ram pressure models fit column density gradient better than tidal model (Meurer et al. 1985, Moore & Davis 1994)

5. Background Recent Observations HIPASS survey of Stream Leading Arm discovered (Putman et al. 1998) First high spatial resolution look at the Stream Bifurcation in Stream (Putman et al. 2003) One of the tidal arms coming from LMC connects to the Leading Arm (Staveley- Smith et al. 2003) First high velocity resolution look at the Stream (Brüns et al. 2005) Putman et al. 1998 Putman et al. 2003 Brüns et al. 2005

6. Background Recent Models Ram pressure models can reproduce most observations. But no Leading Arm (Mastropietro et al. 2004) Tidal models reproduce correct Leading Arm shape & bifurcation, Stream bifurcation (LMC crashed through Stream) (Connors et al. 2005) Connors et al. 2005 ObservationsModel Mastropietro et al. 2004

7. Tidal Model Ram Pressure Model Leading Arm X N(HI) gradient X Bifurcation ? No Stars X? ?

8. Leiden/Argentine/Bonn (LAB) all-sky HI survey Combination of Leiden/Dwingeloo Survey with the Instituto Argentino de Radioastronomia Survey (Kalberla et al. 2005) Stray radiation correction First HI all-sky survey. Velocity coverage: –450 < V LSR < +400 km/s. Spatial resolution: 0.5°, velocity resolution: 1.3 km/s, rms T B = 0.09 K Kalberla et al. 2005

9. Gaussian Decomposition of LAB Data GOAL: Want to simplify datacube (e.g. ~260,000 HI spectra) and make it easier to following features that overlap in velocity. Need an automated Gaussian decomposition program Used an algorithm similar to the one presented in Haud 2000 Add Gaussians one at a time Add the Gaussian that reduces the RMS of residuals the most Stop adding Gaussians once RMS of residuals ≈ noise level

10. Database of Gaussians Decomposed the whole LAB database Ran for several weeks on multiple computers Final Results: Whole sky decomposed into 1,375,993 Gaussians Average Decomposition Velocity Brightness Temperature

11. Latitude Longitude

12. Velocity Longitude

13. Latitude Longitude

14. Velocity Latitude

15. High Velocity Clouds

16. Cleaning out the zero-velocity region Putman et al. 2003 and Brüns et al. 2005 had difficulty separating Stream from local gas at V≈0 km/s Can use the Gaussians to do the separation. Use continuity in: space velocity Gaussian width Gaussian height Velocity Galactic Longitude

17. Magellanic Stream Use a coordinate system that bisects the Stream Magellanic Longitude Magellanic Latitude

18. 3D Animation of Magellanic System HI

19. Velocities Plotting the Gaussian centers enhances the structures. Two filaments at the head of the Stream. One filament can be tracked to the LMC Other filament probably comes from the SMC/Bridge region Magellanic Longitude Velocity Latitude

20. SMC/Bridge filament LMC filament LMC SMC Bridge Magellanic Longitude Velocity

21. after velocity mask ATCA & Parkes Hires HI Kim et al. 2003 267 km/s LMC filament originates in the 30 Dor Region Can track the LMC filament back to its origin in the 30 Dor region using velocity cuts Birthplace of the Magellanic Stream Site of extreme star formation. Rich in HI, CO, Hα, GMCs and young stellar clusters Magellanic Longitude Magellanic Latitude NAN TEN CO Yama guchi et al. 2001

22. Distinctive Sinusoidal Pattern What’s causing it? LMC & SMC tumbling about each other? Velocity Magellanic Longitude

23. Are the Filaments Wrapping Around Each Other? If the filaments are wrapping each other, Could show that the LMC and SMC are bound to each other. Could be used to trace the dynamical history of the LMC & SMC system. Magellanic Longitude Velocity

24. Filaments Are Not Wrapping! Filaments are NOT wrapping. LMC filament spiraling on its own SMC/Bridge filament has a smaller scale spiral Velocity→

25. Distinctive Sinusoidal Pattern Possibly imprint of the LMC rotation curve. Can estimate drift rate: Velocity Amplitude: 23 km/s Radius: 2.5°→2.2 kpc Period: 0.6 Gyr Drift Rate: ~30 km/s Age of Stream: ~3 Gyr Velocity Magellanic Longitude

26. Magellanic Latitude Distinctive Sinusoidal Pattern Possibly imprint of the LMC rotation curve. Can estimate drift rate: Velocity Amplitude: 23 km/s Radius: 2.5°→2.2 kpc Period: 0.6 Gyr Drift Rate: ~30 km/s Age of Stream: ~3 Gyr

27. Sinusoidal pattern mysteriously ends ~30° from the LMC edge the sinusoids end Something dramatic must happen there Possibly crossing the LMC tidal radius Mũnoz et al. 2006 found LMC stars at 22° from LMC center Linear portion with smaller spirals/sinusoids Maybe interacting with MW halo gas, drag causing linear trend, damping the sinusoids sinusoid ends linear Magellanic Longitude Velocity

28. Stars Associated with the LMC Filament MC Clusters from Bica et al. 1999 Bluest stars from Irwin, Demers & Kunkel 1990

29. Leading Arm Staveley-Smith et al. 2003 point out: Arm E points towards the Leading Arm Deep HIPASS shows Arm E is continuous with Leading Arm Most Leading Arm gas comes from SMC. Staveley-Smith et al. 2003

30. Leading Arm Magellanic Longitude Velocity LA 1 LA 2 & 3

31. Leading Arm Putman et al. 1998 (discovery paper) showed that the first two concentrations of LA 1 are (nearly) CONTINUOU S

32. Origin of the Leading Arm The Leading Arm complex closest to the LMC (LA 1) connects with the LMC in SPACE and VELOCITY Where does it originate? Magellanic Latitude Velocity On the Sky

33. Origin of the Leading Arm With a velocity cut, we can track LA to its origins Once again, 250 < V LSR < 320 km/s The 30 Dor Region!! Magellanic Longitude Magellanic Latitude ATCA & Parkes hi-res HI Kim et al. 2003 267 km/s

34. Leading ArmLMC Filament 30 Dor Region Kim et al. 2003 LMC filament & Leading Arm originate from the 30 Dor region. Leading Arm also shows signs of periodic motion (spatially). Both periodic motions probably have same cause The Leading Arm is NOT coming from SMC! The 30 Dor Region Filaments 267 km/s

35. Leading ArmLMC Filament 30 Dor Region Staveley-Smith et al. 2003 LMC filament & Leading Arm originate from the 30 Dor region. Leading Arm also shows signs of periodic motion (spatially). Both periodic motions probably have same cause The Leading Arm is NOT coming from SMC! The 30 Dor Region Filaments

36. Magellanic Longitude Velocity

37. Magellanic Longitude Velocity Magellanic Latitude

38. Velocity another filament? Magellanic Stream Leading Arm LMC filament

39. Can Track both filaments all the way along Stream Well separated either in velocity or spatially. Use space-velocity cuts for upper part of the Stream Spatial cuts for the lower part of the Stream LMC filament SMC/Bridge filament

40. Tidal Model Ram Pressure Model Leading Arm X N(HI) gradient X Bifurcation X? No Stars X? ? LMC filament ? SMC filament ?

41. Conclusions Gaussian decomposition of entire LAB survey. First thorough analysis of the velocities of the Stream: Found the origins of the Stream Two filaments at head of Stream, one from LMC (30 Dor), other from SMC/Bridge region LMC filament has distinctive sinusoidal pattern that ends abruptly Filaments do not wrap around each other (at head of Stream) Leading Arm also originates in 30 Dor region

42. Conclusions Can track both filaments all the way along the Stream Stars associated with the LMC filament Thus the Magellanic Stream provides new and powerful constraints for models of the SMC-LMC-Milky Way interaction. These findings will be submitted for publication soon

43. Thank You!