VIEWS: 4 PAGES: 11 POSTED ON: 11/28/2012
Semi-analytic Models based on Millennium II Haloes 富坚 1 Introduction to Millennium II Simulation • Michael Boylan-Kolchin et al. 2009 • The comparison between Millennium I and Millennium II: higher resolution Millennium I Millennium II Mini-Millennium II Particle number 21603 4323 Particle Mass 8.6×108M☉h-1 6.8×106 M☉h-1 8.6×108M☉h-1 Box size 500 h-1 Mpc 100 h-1 Mpc 100 h-1 Mpc Output snapshots 64 snapshots 68 snapshots Between z=0 and 127 Between z=0 and 127 Minimum halo mass 1.7×1010M☉h-1 1.4×108M☉h-1 1.7×1010M☉h-1 • Mini-Millennium II: same resolution as Millennium I but same box size as Millennium II • http://www.g-vo.org/MyMillennium3/ sql queries for Millennium II halo tree data 2 The halo mass functions between MI and MII simulations 3 The semi-analytic models • The L-Galaxies models based on Millennium I haloes by De Lucia et al. 2007 Stellar mass function from L-Galaxies at z=0 • The inconsistency for the merger history of haloes smaller than Mhalo~1011 M☉ at z=0 • Resolution effect for galaxies smaller than M* ~109.5 M☉ • Both the results based on Millennium I and II haloes predict too much small galaxies 4 The semi-analytic models • The models by Guo Qi et al. 2010 aims to solve the problem of too much small galaxies from the model results • The changes to L-Galaxies model: 1.supernova feedback recipes ESN 0.5òhalo m*vSN 2 òhalo : the proportion of sn energy to reheat the gas mreheat òdisk m* disk cold gas halo hot gas meject 2 ESN Ereheat / vvir 2 2 vSN òhalo m* 2 mreheat halo hot gas ejected gas if meject 0 vvir De Lucia's recipe: òhalo =0.35 and òdisk =3.5 are constants. Guo's recipe: òdisk ò 0.5 vmax / 70km s 1 òhalo 0.5 vmax / 70km s 1 1 2 ò 6.5 0.32 1 2 3.5 6 The semi-analytic models • The changes to L-Galaxies model: 2. reincorporation recipe mreincorporate mejected ejected gas reincorporated back into halo t halo tdyn De Lucia's recipe: 0.5 vvir Guo Qi's recipe: 0 0 0.3 220 km/s 3. other changes gas stripping, satellite disruption disk size recipes gas,* r 0 exp r / Rd gas,* gas,* Trace the change of angular J gas,* momentum in gas infall, star Rd gas,* 2M gas,*vdisk formation, bulge formation, galaxy merger etc… 7 The mass functions at z=0 from Guo Qio’s model compared to the observational results 0 -1 -2 -3 -4 Obreschow et al. 2009 results based on MI haloes -5 results based on MII haloes -6 8.5 9 9.5 10 10.5 8 H2 formation and star formation processes in Millennium II haloes • Migrate my previous codes based on Millennium I haloes to Millennium II haloes • Include the multiple ring • Include the H2 formation processes to get HI and H2 components in Millennium II simulation • Star formation rate SFR H 2 • Get the redshift evolution of gas (neutral and molecular), i.e. MZ relation as a function of z 9 Inconsistency for the results from different halo resolutions 10 The reason for the inconsistency from different halo resolutions • No gas consumption or metal production in small haloes based on Millennium simulation • The H2 proportional star formation law is more sensitive to the gas metallicity than Guo Qi and De Lucia’s recipe SFR M gas M crit • Inconsistency: earlier star formation processes in Millennium II scenario metallicity → H2 → star formation → gas consumption • Possible solution: decrease the H2 formation rate in small galaxies/haloes change the supernova feedback 12 Thank you! 13
"Semi-analytic Models based on Millennium II Haloes"