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Are Fast Rotating Galactic Bars a Problem for Cosmology?

Are Fast Rotating Galactic Bars a Problem for Cosmology?. Octavio Valenzuela New Mexico State University. What do we know about the Universe?. Hubble Law (As further a galaxy is, as faster it moves away, Universe Expands)

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Are Fast Rotating Galactic Bars a Problem for Cosmology?

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  1. Are Fast Rotating Galactic Bars a Problem for Cosmology? Octavio Valenzuela New Mexico State University

  2. What do we know about the Universe? • Hubble Law (As further a galaxy is, as faster it moves away, Universe Expands) • Cosmic Microwave Background Radiation (CMBR, Hot Big-Bang) • H, D, He, Li ( Hot Big Bang + Adiabatic Expansion, n,p,e) • Structure in the Universe(Galaxies, Groups of Galaxies, Clusters of Galaxies): Primordial Seeds • Fluctuations in the Temperature of CMB: The seeds?

  3. Hubble Law (As further a galaxy is, as faster it moves away, Universe Expands)

  4. Cosmic Microwave Background Radiation (CMBR, Hot Big-Bang) • Are the fluctuations in CMBR the Seeds of Structure?

  5. H, D, He, Li: Hot Big Bang + Adiabatic Expansion (Universe Cools down). There are n,p,e

  6. Structure in the Universe: Galaxies, Groups, Clusters, Filaments: Primordial Seeds

  7. Zooming in the Cosmic Structure

  8. Bars

  9. Bars

  10. Bars: Milky Way

  11. Bars: Not always Easy to Detect~ 70% of Spiral Galaxies Show Bars

  12. Bars: Dwarfs NGC6822 NGC 3109

  13. Bars: Observations • Bars Size is Comparable to the Characteristic Disk Size: (Elmegreen & Elmegreen 1985 ,Erwin 2003)

  14. Rotation of Bars • Quantified by R= Rc/Rb: Rc: radius where disk and bar rotate at the same speed. Rb: Bar size • R>= 1 (Bars do not rotate faster than disks) • R<1.8 Bars are fast rotators

  15. Rotation of Bars • Direct Method: Using stellar velocities and surface density (Almost only early type galaxies) • Indirect Methods: Dust Lanes (Shocks), Rings (2-D, Gas properties)

  16. Bar Formation • A self-gravitating (heavy) disk is unstable to the formation of a bar Valenzuela & Klypin 2003

  17. Effect of Temperature and Numerical Resolution (VK 2003) • Right Hand Disk is Colder and for the same time presents a Longer and Stronger Bar. • Left hand side bar is 1.5 times the radial exponential disk scale lenght.

  18. Effect of Temperature and Numerical Resolution (VK 2003) • Bars in colder disks are Slower, Longer and Stronger

  19. Evolution of Bars (VK 2003) • A1 and A2 are almost identical models: A1 has a hotter center. • B is a heavy(maximal) disk model. • C is an intermedia case with high resolution (sampling is equivalent to a 3E7 particles simulation)

  20. Bar Rotation (Valenzuela & Klypin 2003) • A1: R= • A2: R= • B: R= • Gerssen etal. 2003

  21. Bar Size (Valenzuela & Klypin 2003) • Rinit = 3.5 kpc Rfinal= 4.0 kpc Rbar = 4.1 kpc • Rinit = 3 kpc Rfinal = 5.1 kpc Rbar = 4.5 kpc • Gerssen etal. 2003

  22. Summary • It is possible to get Realistic (short and fast rotating) bars inside cosmological motivated dark matter halos. • Md/Mh and strength of random motions seem to drive bar and perhaps disk evolution. Colder disks and halos are more resonant and enhance the angular momentum tranfer from the bar(spiral arms) to outer disk and halo.

  23. Open Questions • Can the abundance of bar galaxies benn predicted by Cosmological Models? • Can the distributions of Bar sizes and Speeds been predicted by Cosmology? • How abundandt are Barred Galaxies?

  24. Graphics

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