Modeling the dependence of galaxy clustering on stellar mass and SEDs Lan Wang Peking University Collaborators: Guinevere Kauffmann (MPA) Cheng Li (MPA/SHAO,USTC) Gabriella De Lucia (MPA)

Link galaxy properties to DM halos Hydrodynamic Simulation e.g. White, Hernquist & Springel 2001 Semi-analytic models Kauffmann et al. 1999 Halo Occupation Distribution models (HOD) Berlind & Weinberg 2002 Yang, Mo & van den Bosch 2003

Our Methodology Falls in between semi-analytic & HOD approach: Positions, velocities and formation history from simulation Parameterized functions to determine galaxy properties Millennium simulation

Two steps： Minfall - halo mass at infall time tinfall ‘Orphan’ galaxies – satellites without subhalos vs. HOD: halo mass of today Two steps： Minfall →Mstars tform, tinfall →SFH →Dn4000

Mstars vs. Minfall in semi-analytic catalogue Croton et al. 2006

Statistics reproduced vs. semi-analytic results Stellar mass Function Correlation

‘orphan’ galaxies Critical for correlation at small scales

Application to SDSS Fit stellar mass function & clustering for different stellar mass bins Separate relations for central/satellite give better fit

Fitted relations Satellites are less massive than centrals Mandelbaum et al. 2006 Satellites are less massive than centrals

SDSS observation

tform tinfall tpresent Modeling SEDs Exponentially evolved SFR with time scales and central satellite BC03 Log(SFR) Dn4000 + Mstars positions tform tinfall tpresent

Best-fit: Constant SFR:

Main results Massive centrals have ceased forming stars At low stellar masses, central galaxies display a wide range of different SFH, with a significant fraction experiencing recent star bursts. Time scale for satellite galaxies is almost independent of stellar mass

SFH: compared with SAM (De Lucia & Blaizot 2007) e-folding time scales for satellites our model: ~2-2.5 Gyr SAM: ~1Gyr

Evolution to higher redshifts Dn4000 – local density relation VVDS & DEEP2 Cucciati et al. 2006 Cooper et al. 2006 redshift: 0.3 0.8 1.5 2 3

Conclusions A new statistical model of galaxy clustering Double power-law form for Mstars ~ Minfall relation Applied to SDSS: For a given Minfall, satellites are less massive than centrals Clustering dependence on SEDs reproduced Massive central galaxies have ceased forming stars; At low stellar masses, a significant fraction of central galaxies have recent starbursts Satellite galaxies of all masses have declining SFR, with

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