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Rotation of Cosmic Voids (Lee & Park 2006, ApJ in press, astro-ph/0606477)

Rotation of Cosmic Voids (Lee & Park 2006, ApJ in press, astro-ph/0606477). Jounghun Lee & Deaseong Park (Seoul National University). OUTLINE. Origin and properties of voids Questions about voids yet to be answered A new nonparametric model for voids key assumptions analytic predictions

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Rotation of Cosmic Voids (Lee & Park 2006, ApJ in press, astro-ph/0606477)

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  1. Rotation of Cosmic Voids(Lee & Park 2006, ApJ in press, astro-ph/0606477) Jounghun Lee & Deaseong Park (Seoul National University)

  2. OUTLINE • Origin and properties of voids • Questions about voids yet to be answered • A new nonparametric model for voids • key assumptions • analytic predictions • numerical tests • Discussion & conclusion • Ongoing & future works

  3. Clusters d(x) x Voids Origin of Voids and Clusters • Local extrema of the primordial density field

  4. Properties of Voids • Occupying 40% of the cosmic volume (Hoyle & Vogeley 2004) • Extremely underdense: dV ~ -0.9 • Expanding faster • Containing bluer galaxies with higher SFR (Hoyle et al. 2005) (2dFGRS, Hoyle et al. 2005)

  5. Unresolved Issues • Why are voids non-spherical ? • Not intuitive due to the very fact that they have low-density and undergo faster expansion • Why are void galaxies bluer with high SFR? • Not explained by the density-morphology relation (Hoyle et al. 2005)

  6. Clues from Previous Works • Shandarin et al (2006, MNRAS, 367, 1629) • Identifying voids using the excursion set approach in high-resolution simulations • Quantified the nonsphericity of voids • Suggesting that voids undergo stronger tidal effect

  7. Linear Tidal Torque Theory • Alignments between the spin axes and the intermediate principal axes of the local tidal tensors • Aspherical shapes of protohalos • Misalignments between the tidal and the inertia tensors

  8. A New Theory • Clusters form in the regions where the degree of alignment between T and I is strongest. • Less vulnerable to the tidal effect • Low spin-generation efficiency • Voids form in the initial regions where the degree of misalignment between T and I is weakest • More vulnerable to the tidal effect • High spin-generation efficiency

  9. Spin Generation Efficiency

  10. Tidal Effect on Voids • Generating the rotation of matter that make up voids around the center of mass. • Inducing the strong alignments between the void spin axis and the intermediate principal axis of local tidal tensor

  11. Key Prediction I • Correlations between the spin axes of neighbor spins

  12. Key Prediction II • Anti-correlations between the spin axes of voids and the directions to the nearest voids

  13. Void Spin-Spin Correlations

  14. Void Spin-Direction Correlations

  15. Finding Voids from Simulations • The Millennium-Run Galaxy Catalog • 21603 particles • Linear size of 500 Mpc/h • LCDM Cosmogony • 8964936 galaxies at z=0 • The Void-Finder by Hoyle & Vogeley (2002, ApJ, 566, 641) • 24037 voids with Ng > 30

  16. Measuring Void Spin

  17. Void Density Distribution

  18. Void Spin Parameter Distribution

  19. Analytic vs. Numerical I

  20. Analytic vs. Numerical II

  21. Discussion • Strong tidal effect on voids • Deviate void shapes from spherical symmetry • The less massive, the higher degree of triaxiality • Transfer high angular momentum to void galaxies • Block gas cooling • Delay star formation • Explain the high SFR and bluer colors of void galaxies:

  22. Summary and Conclusion • Constructing a new theory for cosmic voids • Quantifying the tidal effect on the voids • Void spin-spin correlation • Void spin-direction anti-correlation • Providing a quantitative physical explanations to the observed properties of voids • Providing a new insight to the large-scale matter distribution in a cosmic web

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