1. 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)

2. 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

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

4. 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

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

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

7. ‘orphan’ galaxies
Critical for correlation at small scales

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

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

10. SDSS observation

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

12. Best-fit:
Constant SFR:

13. 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

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

15. 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

16. 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

17. Thank you !