gustavo yepes universidad autónoma de madrid knaw international colloquium on cosmic voids...
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Gustavo YepesUniversidad Autónoma de Madrid
KNAW
International Colloquium on COSMIC VOIDS
Amsterdam 2006
COLLABORATORSCOLLABORATORS
Matthias Hoeft (IU. Bremen)Matthias Hoeft (IU. Bremen)
Stefan Gottlöber (AIP)Stefan Gottlöber (AIP)
Volker Springel (MPG)Volker Springel (MPG)
CDM Mass function in void regionsCDM Mass function in void regions
High-resolution N-body Simulations Gottlöber et al 2003
The missing dwarf galaxy The missing dwarf galaxy problem in void regionsproblem in void regions
● If If CDM comology is correct there should be a lot of small halos CDM comology is correct there should be a lot of small halos (Vc < 20 km/s ) in voids. Same problem as satellites of galaxies: (Vc < 20 km/s ) in voids. Same problem as satellites of galaxies: too much substructure in CDM models.too much substructure in CDM models.
● No galaxies brighter than MNo galaxies brighter than MBB=-11 (Karanchentsev talk) found in =-11 (Karanchentsev talk) found in local voids.local voids.
● What happens with baryons of small halos in voids?What happens with baryons of small halos in voids?– Are they visible but very faint?. Magnitude, colors. (Red Dwarfs)Are they visible but very faint?. Magnitude, colors. (Red Dwarfs)– Are they just baryonless dark halos?Are they just baryonless dark halos?
● What are the physical mechanisms ?What are the physical mechanisms ?– Gas evaporation by UV photoionization Gas evaporation by UV photoionization – Supernova feedback (e.g Dekel & Silk) Supernova feedback (e.g Dekel & Silk)
● What is the typical halo mass for this to happen?What is the typical halo mass for this to happen?
GALAXY FORMATION GALAXY FORMATION IN VOIDS IN VOIDS
M. Hoeft, G. Yepes, S. Gottlober and V. Springel, M. Hoeft, G. Yepes, S. Gottlober and V. Springel, MNRAS 2006, 371, 401MNRAS 2006, 371, 401
And And Matthias Hoeft’s talk tomorrowMatthias Hoeft’s talk tomorrow
HIGH RESOLUTION HIGH RESOLUTION CDM CDM VOID SIMULATIONS VOID SIMULATIONS
MULTIMASS TECHNIQUEMULTIMASS TECHNIQUEMulti-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
(G)ASTROPHYSICAL (G)ASTROPHYSICAL PROCESSESPROCESSES
● 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.
VOIDS FROM A 80/h Mpc Box
1024102433 effective particle in void region effective particle in void region MMgas gas = = 5.5106 M MMdark dark = = 3.4107 M Smoothing= 2 kpcSmoothing= 2 kpc
20/h Mpc20/h Mpc Simulations done with GADGET2Simulations done with GADGET2Primordial CoolingPrimordial CoolingPhotoionization Photoionization Multiphase mediumMultiphase mediumStar formationStar formationFeedback Feedback ThermalThermal Kinetic (Winds)Kinetic (Winds)
15/h Mpc15/h Mpc15/h Mpc15/h Mpc
Void with 10243 effective particles (7 million particles )
– Mgas = 1.5106 M
– Mdark= 8.2106 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
(ULTRA)HIGH-RESOLUTION (ULTRA)HIGH-RESOLUTION SIMULATIONS OF VOIDS SIMULATIONS OF VOIDS
50/h Mpc Box 50/h Mpc Box
10/h Mpc10/h Mpc
Different feedback parametersDifferent feedback parameters
List of simulationsList of simulationsHoeft et al 2006, MNRAS Hoeft et al 2006, MNRAS 371, 401Hoeft et al 2006, MNRAS Hoeft et al 2006, MNRAS 371, 401
++Simulations with Kinetic Feedback (stellar winds)Simulations with Kinetic Feedback (stellar winds)
With different values of With different values of (fraction of E(fraction of ESNSN that goes into wind that goes into wind
++Simulations with Kinetic Feedback (stellar winds)Simulations with Kinetic Feedback (stellar winds)
With different values of With different values of (fraction of E(fraction of ESNSN that goes into wind that goes into wind
Halo Mass function in VoidsHalo Mass function in Voids
Baryon fractionBaryon fraction
Halos belowfew times109 Msun
arebaryon-poor
Characteristicmass scaledepends onredshift
Characteristic Mass of UV evaporationCharacteristic Mass of UV evaporation
Characteristic massCharacteristic mass Mc
baryon-rich
baryon-poor
Mc risessignificantlywith z
Halo may startbaryon-richand becomelaterbaryon-poor
Tentry
What is the characteristic Mass?What is the characteristic Mass?
Listen to Matthias Hoeft’s talk tomorrowListen to Matthias Hoeft’s talk tomorrowDensity –Temperature phase diagramDensity –Temperature phase diagram
Cold mode of galactic gasaccretion: gas creeps alongthe 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.
New Filtering Mass EstimateNew Filtering Mass Estimate(M. Hoeft’s talk tomorrow)(M. Hoeft’s talk tomorrow)
Smoothing of baryonicSmoothing of baryonicFluctuations due to Fluctuations due to counteracting pressure counteracting pressure gradiantsgradiants
MMf f = = 4/3 22a/ka/kff))33
Mass accretion histories and Mass accretion histories and gas condensation in void halosgas condensation in void halos
MMcc
Age of stars in void halosAge of stars in void halos
In small halosstars can onlybe formed at highredshift
Stellar mass functionStellar mass function
Thermal feedbackThermal feedback
Mass-Luminosity functionMass-Luminosity function
z=0z=0
Bruzual & Charlot 03
SPSM
Thermal feedbackThermal feedback
Strong wind modelStrong wind model
Mass-Luminosity functionMass-Luminosity function
z=0z=0
Cum. Luminosity functionCum. Luminosity functionCum. Luminosity functionCum. Luminosity function
High ResolutionHigh ResolutionBasicBasic
Small WindsSmall Winds
Luminosity functionLuminosity functionLuminosity functionLuminosity function
Wind 0.15Wind 0.15
Wind 0.05Wind 0.05
Wind 0.4 Wind 0.4
Wind 0.25Wind 0.25
Kinetic Feedback: Kinetic Feedback: Energy in windsEnergy in winds
Luminosity functionLuminosity functionLuminosity functionLuminosity function
Effects of UV fluxEffects of UV fluxEffects of UV fluxEffects of UV flux
UV=0UV=0UV=0UV=0
UV*100UV*100UV*100UV*100
UV*0.1UV*0.1UV*0.1UV*0.1
UV*10UV*10UV*10UV*10
UV*0.01UV*0.01UV*0.01UV*0.01
COLOR-MAGNITUDE
COLOR-MAGNITUDEUV Normalization
COLOR-MAGNITUDEUV Normalization
COLOR-MAGNITUDEUV Normalization
COLOR-MAGNITUDEWind Energy
COLOR-MAGNITUDEWind Energy
Filtering Mass at z=0
McMcMcMc
Mean age of starsMean age of starsMean age of starsMean age of stars Mean Metallicity of starsMean Metallicity of starsMean Metallicity of starsMean Metallicity of stars
DWARF GALAXIES IN GROUPS:Same resolution than void
simulations (10243 effective)11.5 million total particles
4.5 million gas4.5 million high-res dark
Dwarfs in voids and groupsDwarfs in voids and groups
CONCLUSIONS 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 CDM .
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.
THANK YOU
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http://astro.ft.uam.es/marenostrum
• MareNostrum Universe SimulationMareNostrum Universe Simulation:2x10243 500/h Mpc SPH
• MN High z Galaxy Formation SimulationMN High z Galaxy Formation Simulation:
2x10243 50/h Mpc SPH +gastrophysics • MN Local Universe Constrained SimulationsMN Local Universe Constrained Simulations
• 2x10243 64 to 320/h Mpc boxes N-body , SPH+gastrophysics
Commercial (Free of charge):Commercial (Free of charge):
MNCPMNCPThe MareNostrum Numerical Cosmology ProjectThe MareNostrum Numerical Cosmology Project
http://astro.ft.uam.es/marenostrum
• MareNostrum Universe SimulationMareNostrum Universe Simulation:2x10243 500/h Mpc SPH
• MN High z Galaxy Formation SimulationMN High z Galaxy Formation Simulation:
2x10243 50/h Mpc SPH +gastrophysics • MN Local Universe Constrained SimulationsMN Local Universe Constrained Simulations
• 2x10243 64 to 320/h Mpc boxes N-body , SPH+gastrophysics