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‘GoldenEye’ in action: Mapping the Galaxy with GALFA Snežana Stanimirović (UW-Madison)

‘GoldenEye’ in action: Mapping the Galaxy with GALFA Snežana Stanimirović (UW-Madison). “GoldenEye” (1995): the 17th James Bond movie. At the end of “GoldenEye” James Bond goes to Puerto Rico searching for a gigantic satellite dish…. …And he finds the 305-m Arecibo radio

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‘GoldenEye’ in action: Mapping the Galaxy with GALFA Snežana Stanimirović (UW-Madison)

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  1. ‘GoldenEye’ in action: Mapping the Galaxy with GALFASnežana Stanimirović (UW-Madison)

  2. “GoldenEye” (1995): the 17th James Bond movie At the end of “GoldenEye” James Bond goes to Puerto Rico searching for a gigantic satellite dish…

  3. …And he finds the 305-m Arecibo radio telescope, the largest radio telescope in the world! “The Arecibo Observatory is part of the National Astronomy and Ionosphere Center (NAIC), a national research center operated by Cornell University under a cooperative agreement with the National Science Foundation (NSF).” Built in 1963 but still lots of exciting scientific capabilities….

  4. In this talk: What do we know and don’t know about the Galactic Halo How do we study Galactic Halo GALFA survey in a nutshell: Why? How? Science Highlights: 1. The MagellanicStream 2. “Bucky galaxy”

  5. Artist: Jon Miller Artist: Ron Miller

  6. A more schematic view of dramatic “links” btw the Galactic disk and halo Galactic disk h~650 ly ~130,00 ly Hot Galactic Halo, or corona @200,000 ly

  7. Most of the Galactic gas is in the form of atomic hydrogen (or HI) and can be mapped by radio telescopes Leiden/Argentine/Bonn survey 36 arcmin resolution Most of this gas belongs to the Galaxy. However…

  8. ~40% of sky is covered by “clouds” that do not take part in Galactic rotation High Velocity Clouds (HVCs) Wakker, UW Madison Magellanic Clouds Magellanic Stream

  9. We don’t know where HVCs come from, but we know that: • Supernovae blow large holes in the Galactic disk • Some gas is being grabbed from our neighbors…. • The Galaxy has a large hot corona through which HVCs move • -> Disk & Halo must be talking to each other…. McClure-Griffiths et al. (2006)

  10. the most spectacular example of disk-halo interaction… Artist: Jon Miller @ 60 kpc or 200,000 ly Artist: Ron Miller

  11. b=-45deg Tip of The Stream b=-40deg Stream in HI: Parkes HI observations (15’ resolution) Stream Bridge SMC Parkes radio telescope Australia Dish Diameter = 64 m Leading Arm LMC

  12. b=-45deg Tip of The Stream b=-40deg Stream in HI: Parkes HI observations (15’ resolution) Stream At Dec~0 deg chaotic network of filaments and clumps Two double-helix filaments Bridge SMC Mathewson & Ford (1984, IAU Symp. 108) Leading Arm LMC Putman et al. (2003)

  13. What we want to find out: • How do Galactic disk and halo exchange matter? • What’s the internal structure of the Galactic Halo? • How do galaxies like the Milky Way harass their neighbors? • How do galaxies like the Milky Way accrete gas ? • Can we trace infalling gas from the halo into the disk? These questions are important for our own Galaxy but for far-away galaxies as well! Need: large-area surveys with high angular resolution to zoom in on the disk-halo interactions! … and that’s what GALFA is about ! GALFA = Galactic Science with ALFA International collaboration (~80 members) @www.naic.edu/alfa/galfa/

  14. Luckily James Bond saved the GoldenEye. In fact, the GoldenEye is more powerful than ever because of ALFA...

  15. ALFA andwhat do we measure with a radio telescope?

  16. ALFA = Arecibo L-band Feed Array … To survey the sky much faster!

  17. The 21-cm line of atomic hydrogen every 107 years Cosmos: The Swinburne Astronomy Online Encyclopedia Hydrogen atom

  18. Measuring Motions: Spectral Line Maps Modified from Alyssa Goodman

  19. Velocity from Spectroscopy Observed Spectrum Telescope  Spectrometer 1.5 1.0 Intensity 0.5 All thanks toDoppler. Hotter gas  faster motions of H atoms  Broader spectral line 0.0 Radial Velocity in km/sec -0.5 100 150 200 250 300 350 400 Modified from Alyssa Goodman "Velocity"

  20. GALFA’s “art”: covering the whole sky visible from Arecibo Effective integration time per pointing

  21. Why is Arecibo + ALFA so special for Galactic science ? A very unique combination: Large bucket, or “Sensitivity” Big dish, or “Good resolution (3’)” A single big dish, or “Full spatial frequency coverage” AC0 HVC -- LDS AC0 HVC -- GALFA

  22. What do we find?

  23. b=-45deg Tip of The Stream b=-40deg Stream in HI: Parkes HI observations (15’ resolution) Stream At Dec~0 deg chaotic network of filaments and clumps Two double-helix filaments Bridge SMC Mathewson & Ford (1984, IAU Symp. 108) Leading Arm LMC Putman et al. (2003)

  24. The Magellanic Stream: Velocity Field:400 (Clouds) to -400 (tip) km/s b=-25 b=-50 SMC LMC GALFA-HI image: ~900 deg2 3’ resolution, N=3x1018 cm-2 (3-, v=20 km/s) Putman et al. (2003)

  25. How extended is the northern MS?4 GALFA ‘filaments’ +5 ‘filaments’ in HIPASS || to MS to LMC “Secondary Streams”: Westmeier & Koribalski 08

  26. Milky Way SMC LMC Connors et al. (2006)

  27. Connors et al. (2006): detailedspatial structure of the Stream can be reproduced by gravitational interactions Leading arm 2 younger streams Main ‘stream’ bifurcated Bridge But, specific encounters needed! SMC Stream Very distant stream

  28. But there is all this clumpy structure…. Samantha’s catalog of ~180 clouds: N(HI), angular size, velocity profiles. Cross-correlated with catalogs of HVCs and mini-HVCs “purely” MS sample Samantha Hoffman UW undergrad. student

  29. Spatial and Velocity structure along the MS • LMC X Putman03 ∆ GALFA ram pressure new tidal old tidal We can compare velocity of Stream clouds with predictions from various models.  Gravity is doing ok, but need to think about additional processes

  30. ~15% of clouds have multi-phase (warm & cold gas) structure • “Cold cores”: • FWHM ~13 km/s • (range 3 to ~20 km/s) • “Warm envelopes”: • FWHM ~25 km/s • Multi-phase medium • Narrow line means cooler gas • Broader line means warmer gas • And all this happening 60 kpc away from us, deep in the Galactic halo Why is this interesting?

  31. Challenges theoretical understanding of heating/cooling processes in the Milky Way halo

  32. Summary: • Arecibo radio telescope is surveying the Galaxy with high angular and velocity resolution. • Diverse and rich science case + legacy products for the astronomy community at large. • Already revising ourknowledge about interactions between the Galactic disk and halo. • The Magellanic Stream is more extended (& filamentary) than previously thought. • Our observations favors gravity for explaining new filaments, but new proper motions and/or additional mechanism needed. • Multi-phase medium at large distances requires reconsideration of Halo properties and phase conversion mechanisms.

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