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Are High-Velocity Clouds a Common Feature of Star Forming Galaxies?

Are High-Velocity Clouds a Common Feature of Star Forming Galaxies?. Wakker et al. (2000). HVCs as Local Group Building Blocks?. Grebel 1998. M HI ~ 4.5 D 2 (kpc) Size ~ 0.4 deg 2 N HI ~ 10 19 cm -2. At 5 kpc M HI = 115 M o d HI = 60 pc n HI = 5 x 10 -2 cm -3.

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Are High-Velocity Clouds a Common Feature of Star Forming Galaxies?

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  1. Are High-Velocity Clouds a Common Feature of StarForming Galaxies? Wakker et al. (2000)

  2. HVCs as Local Group Building Blocks? Grebel 1998

  3. MHI ~ 4.5 D2 (kpc) Size ~ 0.4 deg2 NHI ~ 1019 cm-2 At 5 kpc MHI = 115 Mo dHI = 60 pc nHI = 5 x 10-2 cm-3 Compact HVC Typical HI Masses and Sizes At 1 Mpc MHI=4.6 x 106 Mo dHI=12 kpc nHI=2.5 x 10-4 cm-3 At 50 kpc MHI=1.15 x 104 Mo dHI=600 pc nHI=5 x 10-3 cm-3 At 500 kpc MHI=1.15 x 106 Mo dHI=6 kpc nHI=5 x 10-4 cm-3

  4. HVC Distances • Direct methods

  5. Direct Distance Determinations • Large complexes using halo stars • Complex A: 4 - 10 kpc • Complex M: < 4 kpc • Complex WE: < 13 kpc • HVC279-33+120: < 50 kpc • Complex C: > 6 kpc • ~5 other HVCs: > 0.3 kpc

  6. HVC Distances • Direct methods • Ha emission measurements

  7. Compact HVC Ha Detections Ha

  8. HVC Distances • Direct methods • Ha emission measurements • Deep HI observations of groups

  9. Deep Surveys of Groups • Small area in Local Group-like groups, 0 star-free HI objects to 7 x 106 Mo(Zwaan 2001) • Many other surveys of groups down to a few x 107 Mo have also found 0(e.g. Lo et al. 1979, Dahlem et al. 2001) Sculptor Group None to ~107 Mo(Putman et al. 2003) 2% of group, None to 3 x 106 Mo(de Blok et al. 2001) Same for Centaurus A

  10. HVC Distances • Direct methods • Ha emission measurements • Deep HI observations of groups and spiral galaxies • Lya absorbers

  11. HVC Distances • Direct methods • Ha emission measurements • Deep HI observations of groups and spiral galaxies • Lya absorbers • Ionization constraints

  12. Moore et al.(1999)

  13. Incoming Star Formation Fuel? Wakker et al. (2000)

  14. Smooth Accretion of Intergalactic Gas Bryan & Norman Bowen, Pettini & Blades (2002)

  15. Mergers and Satellite Accretion Harding et al.

  16. Galactic Fountain Material

  17. Our Galaxy Putman et al. (2003)

  18. M81 Group (Yun, Ho & Lo 1994)

  19. Leo Ring (Schneider et al. 1981)

  20. Anomalous HI around galaxies • M101 (van der Hulst & Sancisi 1988) • M83 (O. K. Park et al.) • FCC35 (Putman et al. 1998) • NGC 2442 (Ryder et al. 2001)

  21. NGC 2403 (lowest contour ~ 2 x 1019 cm-2; Fraternali et al. 2002)

  22. Questions to be answered • Is there a relation between the presence of HVCs and a galaxy’s star formation rate?

  23. SINGG = Survey for Ionization in Neutral Gas Galaxies (Meurer et al.) This candidate eldot was not detected in follow-up spectroscopy.

  24. NGC 1533 Ryan-Weber et al. (2003)

  25. Questions to be answered • Is there a relation between the presence of HVCs and a galaxy’s star formation rate? • What type of environment are galaxies with HVCs found in? Are there near-by companions? • How are HVCs related to the Ly-limit absorbers which also are commonly found in galaxy halos? And the O VI and lower column Lya absorbers which are often 100s of kpc from a galaxy? • How do HVCs fit into the CDM model of galaxy formation?

  26. Target Selection • Northern extension of HIPASS (d = 2 – 25o ) • Based on number of sources found in southern HIPASS, there should be ~900 sources • Stick to v < 2000 km/s, should be ~300 • ALFA resolution ~10 kpc at 10 Mpc • High-sensitivity mapping of the sample (to NHI~1019 cm-2, r~100 kpc) should provide information on the frequency and location of HVCs

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