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Gustavo Yepes Universidad Autónoma de Madrid

KNAW International Colloquium on COSMIC VOIDS Amsterdam 2006. Simulating galaxy formation in cosmic voids. Gustavo Yepes Universidad Autónoma de Madrid. COLLABORATORS. Matthias Hoeft (IU. Bremen) Stefan Gottlöber (AIP) Volker Springel (MPG). CDM Mass function in void regions.

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Gustavo Yepes Universidad Autónoma de Madrid

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  1. KNAW International Colloquium on COSMIC VOIDS Amsterdam 2006 Simulating galaxy formation in cosmic voids Gustavo Yepes Universidad Autónoma de Madrid

  2. COLLABORATORS Matthias Hoeft (IU. Bremen) Stefan Gottlöber (AIP) Volker Springel (MPG)

  3. CDM Mass function in void regions High-resolution N-body Simulations Gottlöber et al 2003

  4. The missing dwarf galaxy problem in void regions • If LCDM comology is correct there should be a lot of small halos (Vc < 20 km/s ) in voids. Same problem as satellites of galaxies: too much substructure in CDM models. • No galaxies brighter than MB=-11 (Karanchentsev talk) found in local voids. • What happens with baryons of small halos in voids? • Are they visible but very faint?. Magnitude, colors. (Red Dwarfs) • Are they just baryonless dark halos? • What are the physical mechanisms ? • Gas evaporation by UV photoionization • Supernova feedback (e.g Dekel & Silk) • What is the typical halo mass for this to happen?

  5. GALAXY FORMATION IN VOIDS M. Hoeft, G. Yepes, S. Gottlober and V. Springel, MNRAS 2006, 371, 401 And Matthias Hoeft’s talk tomorrow

  6. HIGH RESOLUTION LCDM VOID SIMULATIONS MULTIMASS TECHNIQUE • Multi-mass technique to achieve high resolution: • Re-Simulated void areas from large computational boxes by resampling particles of incresing mass away from the refined region: • Original intial conditions set up to 20483 particles in a big (50-80 Mpc) box. • S. Gottloeber’s void finding algorithm: • Spherical void regions are selected as maximum spheres that do not contain any large (> 2x1011 M)halo

  7. (G)ASTROPHYSICAL PROCESSES • To study in detail the galaxy formation process we take into account: • Radiative and Compton cooling • UV-photoionization • Multiphase ISM. • Star Formation. • Star-Gas back-reactions • SN’s thermal Feedbacks: Cloud Evaporation and gas reheating • Stelar Winds • Springel-Hernquist (2003) implementation of multiphase SPH modeling in GADGET-2.

  8. VOIDS FROM A 80/h Mpc Box 20/h Mpc Simulations done with GADGET2 Primordial Cooling Photoionization Multiphase medium Star formation Feedback Thermal Kinetic (Winds) 10243 effective particle in void region Mgas = 5.5106 M Mdark = 3.4107 M Smoothing= 2 kpc

  9. 15/h Mpc

  10. (ULTRA)HIGH-RESOLUTION SIMULATIONS OF VOIDS 50/h Mpc Box Different feedback parameters Void with 10243 effective particles (7 million particles ) Mgas = 1.5106 M Mdark= 8.2106 M Spatial smoothing= 2 kpc Same void was resimulated with full resolution 20483 ( 43 million particles in total) Mgas  2 105 M Mdark 106 M Spatial smoothing= 0.5 kpc comoving 10/h Mpc

  11. List of simulations Hoeft et al 2006, MNRAS 371, 401 + Simulations with Kinetic Feedback (stellar winds) With different values of h (fraction of ESN that goes into wind h= 0.05, 0.15, 0.25, 0.4

  12. Halo Mass function in Voids

  13. Baryon fraction Halos below few times 109 Msun are baryon-poor Characteristic mass scale depends on redshift

  14. Characteristic Mass of UV evaporation

  15. Characteristic massMc Mc rises significantly with z Halo may start baryon-rich and become later baryon-poor baryon-rich baryon-poor

  16. What is the characteristic Mass? Listen to Matthias Hoeft’s talk tomorrow Tentry Density –Temperature phase diagram Cold mode of galactic gas accretion: gas creeps along the equilibrium line between heating and Cooling (Keres et al. 04) For gas to be able to enter the instabilty branch, need to be heated above Tentry temperature. Mc can be viewed as the critical mass for which the virial temperature of gas inside is above the entry temperature of the thermal unstable regime.

  17. New Filtering Mass Estimate(M. Hoeft’s talk tomorrow) • Smoothing of baryonic • Fluctuations due to counteracting pressure gradiants • Mf = 4/3 p<r>(2pa/kf)3

  18. Mass accretion histories and gas condensation in void halos Mc

  19. Age of stars in void halos In small halos stars can only be formed at high redshift

  20. Stellar mass function

  21. Mass-Luminosity function Bruzual & Charlot 03 SPSM Thermal feedback z=0

  22. Mass-Luminosity function Thermal feedback Strong wind model z=0

  23. Cum. Luminosity function High Resolution Basic Small Winds

  24. Luminosity function Kinetic Feedback: Energy in winds Wind 0.05 Wind 0.15 Wind 0.25 Wind 0.4

  25. Luminosity function UV=0 UV*0.01 UV*0.1 UV*10 UV*100 Effects of UV flux

  26. COLOR-MAGNITUDE

  27. COLOR-MAGNITUDEUV Normalization

  28. COLOR-MAGNITUDEUV Normalization

  29. COLOR-MAGNITUDEUV Normalization

  30. COLOR-MAGNITUDEWind Energy

  31. COLOR-MAGNITUDEWind Energy

  32. Filtering Mass at z=0 Mc

  33. Mean age of stars Mean Metallicity of stars

  34. DWARF GALAXIES IN GROUPS: Same resolution than void simulations (10243 effective) 11.5 million total particles 4.5 million gas 4.5 million high-res dark

  35. Dwarfs in voids and groups

  36. CONCLUSIONS • At present, halos below Mlim~ 7x109 M (vc~27 km/s) are photo-evaporated and have few baryon content, either cold gas or stars. This mass scale decreases with redshift. Very small dependence of UV flux. • Halos can condense baryons and form stars early than reionization redshift. Seems enough for them to shine today. • UV-photoheating not able to suppress most of the small galaxies: Does not solve the problem of excess of substructure of LCDM . • Thermal feedback (as implemented in the simulations) does not play a significant role in keeping gas out of small halos. • Kinetic feedback (winds) is very efficient in suppressing star-formation provided that a substantial fraction of ESN goes into wind energy. Need more work on feedback modeling. • Dwarfs ending up in other environments (e.g groups) have similar properties as long as they have not experience substantial interactions with the host halo.

  37. THANK YOU • Commercial (Free of charge): • MNCP • The MareNostrum Numerical Cosmology Project • http://astro.ft.uam.es/marenostrum • MareNostrum Universe Simulation: • 2x10243 500/h Mpc SPH • MN High z Galaxy Formation Simulation: • 2x1024350/h Mpc SPH +gastrophysics • MN Local Universe Constrained Simulations • 2x10243 64 to 320/h Mpc boxes N-body , SPH+gastrophysics

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