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The Topology of HI in the SMC

The Topology of HI in the SMC. Jeremy Gordon University of Georgia August 2, 2007 Advisors: Dr. Chepurnov Dr. Lazarian. Overview:. Small Magellanic Cloud Genus Statistics HI Column Density Map My Project Results. The Small Magellanic Cloud. NGC 292

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The Topology of HI in the SMC

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  1. The Topology of HI in the SMC Jeremy Gordon University of Georgia August 2, 2007 Advisors: Dr. Chepurnov Dr. Lazarian

  2. Overview: • Small Magellanic Cloud • Genus Statistics • HI Column Density Map • My Project • Results

  3. The Small Magellanic Cloud • NGC 292 • RA 00h52m, Dec -72°50’ • ~60 kpc distant, covers ~ 4.5° x 4.5° area • Knots, filaments, holes, oh my!

  4. Genus Statistics • Initial Developments • 2D Genus – ’89 • G2 = (isolated high-density regions) – (isolated low-density regions) • Mathematically Speaking:

  5. Genus Statistics, Cont. • Random Distribution: • Genus Shift Δν • +Δν ‘swiss-cheese’ topology • -Δν ‘meatball’ topology Kim & Park, 2007

  6. Applications: Turbulence • Studies of turbulence utilize the power spectrum, which contains information on velocity fluctuations • No topological information embedded in the power spectrum, however • Genus analysis is a complementary tool in the study of turbulence

  7. Data and Analysis • Combination of Parkes & ATCAdata • HI: 21 cm line (1420MHz) • Spatial resolution of 29.52”/8.59pc • Effective resolution of ~90”/30pc

  8. HI Column Density Map

  9. Methodology • SMC cropped into 9 overlapping 150x150 regions • ‘Entire’ SMC cropped in 400x300 pixel region • Smoothing scale λ ≤ 10% of image length

  10. Results • 30-75pc: clump topology, trending towards neutral shift

  11. Results • 30-75pc: clump topology, trending towards neutral shift • 75-125pc: neutral/slight positive shift, hole topology

  12. Results • 30-75pc: clump topology, trending towards neutral shift • 75-125pc: neutral/slight positive shift, hole topology • ≥ 125pc: shift becoming more negative, clump topology

  13. 150x150 Regions: Small Scales:30 pc ≤ λ ≤ 50 pc Medium Scales 50 pc ≤ λ ≤ 75 pc Large Scalesλ ≥ 75 pc Similarities & Differences Results, Cont.

  14. 150x150 Results

  15. Conclusion • SMC exhibits a clump topology at small scales • At medium scales, genus shift becomes less negativeneutral/slight positive shift • At large scales, genus shift levels out at a slight negative value • Genus Analysis is an effective, complementary tool in the study of turbulence

  16. References • Gott, J. R., III, Dickinson, M., & Melott, A. L. 1986, ApJ, 306, 341 • Kim, S., & Park, C. 2007, ApJ, 663, 244 • Melott, A. L., Cohen, A. P., Hamilton, A. J. S., Gott, J. R. I., & Weinberg, D. H. 1989, ApJ, 345, 618 • Stanimirovic, S., Staveley-Smith, L., Dickey, J. M., Sault, R. J., & Snowden, S. L. 1999, MNRAS, 302, 417 • Staveley-Smith, L., Sault, R. J., Hatzidimitriou, D., Kesteven, M. J., & McConnell, D. 1997, MNRAS, 289, 225

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