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The Inter-Galactic Populations and Unbound Dark Matter

The Inter-Galactic Populations and Unbound Dark Matter. Ing-Guey Jiang and Yu-Ting Wu National Tsing-Hua University Taiwan. Outline. Introduction The Model The Results Conclusions and Implications. Introduction. Zwicky (1951) found diffuse light between galaxies

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The Inter-Galactic Populations and Unbound Dark Matter

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  1. The Inter-Galactic Populations and Unbound Dark Matter Ing-Guey Jiang and Yu-Ting Wu National Tsing-Hua University Taiwan

  2. Outline • Introduction • The Model • The Results • Conclusions and Implications

  3. Introduction • Zwicky (1951) • found diffuse light between galaxies • imply luminous stars exist between galaxies • many inter-galactic objects are observed • red giant, planetary nebulae, supernovae (Gerhard et al. 2005, Gal-Yam et al. 2003) • Virgo cluster • Durrell et al. (2002): intra-cluster stars could contribute 10%~20% of the total luminosity

  4. Antennae Galaxies J. Hibbard Introduction • one of the scenarios- The Mergers • The galacticmergers

  5. The Model • Stanghellini et al. (2006) • dry mergers of spherical elliptical galaxies • head-on collisions • neglect the dark halo • 5% ~ 20% of the total mass become unbound stars. • Our work: N-body simulation • disc galaxy - disc galaxy • disc galaxy: stellar disc and dark halo

  6. The Model • The galaxy : the stellar disc and dark halo • Density profiles (Hernquist 1993): • disc: • halo: • Parameters:

  7. The parabolic mergers • relative velocity=147.8 km/s • The hyperbolic mergers • relative velocity=273.1 km/s • The separation of the galaxies is 300 kpc (1) (2) (3) (4) (5) (6)

  8. A Disc-Halo System

  9. Virial Ratio of a Merging Event

  10. Model P1: stellar part

  11. Model P1: Dark Matter

  12. Six Parabolic Mergers

  13. Results the parabolic merger the hyperbolic merger

  14. Evolution of Unbound Fractions

  15. Conclusions and Implications • head-on merging events make a considerable fraction of dark matter become unbound • only a tiny fraction of the stellar part become gravitationally unbound • To explain the observed intergalactic populations, multiple mergers and tidal interactions play roles • Some intergalactic populations might be bounded and trapped by dark matter. This implies a definition problem. • Applications: observable population shall give hints on velocity and space distributions of dark matter • Thus, there is a chance to trace Unbound Dark Matter

  16. The End

  17. Computing Facilities • GADGET (Springel et al., 2001) • GAlaxies with Dark matter and Gas intEracT • Parallel Version 1.1 • National Center for High-Performance Computing

  18. The Units G=43007.1 [L]=1 kpc [M]=1010M⊙ [T]=9.8×108 years

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