1. Improved Chemical Evolution Model for the Early Galaxy Evolution 中里直人 東大天文

2. No.2 GENSO (Galaxy EvolutioN with the SPH methOd) Our code for modeling the galaxy evolution GRAPE SPH Chemical Evolution Stellar feedback Cooling function

3. No.3 Initial Model Catalog(1) Public database for researchers –http://pucca.astron.s.u-tokyo.ac.jp/research/model/index.htmlhttp://pucca.astron.s.u-tokyo.ac.jp/research/model/index.html –Program (modified version of GRAFIC), results, and parameter files etc. are all available for public use. 150 full chemo-dynamical models –LCDM cosmology with h = 0.65 –3 sigma sphere –M ~ 5 – 7 10 11 Mo (R ~ 1.5 Mpc) –e gas = e star = 0.5 kpc, e dark = 1.0 kpc –spin parameter ~ 0.1 –z start ~ 24 to z end ~ 1.3 (5 Gyr)

4. No.4 Initial Model Catalog (2) Well fitted disk galaxy : 100 galaxies

5. No.5 Initial Model Catalog (3) Global star formation history

6. No.6 Initial Model Catalog (4)

7. No.7 Problems Too much star formation in early phase –Simple criteria for SF (1) cooling time < dynamical time (2) dynamical time < sound crossing time (3) flow is convergent –Poor numerical resolution (~ a few kpc) Supernova explosions are not effective –Poor numerical resolution Obs. Old model Metallicity distribution function

8. No.8 Star formation scheme (old) SF : converting a SPH particle to a star particle SF model (= Schmit’s law) SPH particle creating a star (SSP) (SSP: single stellar population) decreasing mass of SPH particle ｔ t ＋ dt

9. No.9 Problems in Chemodynamics “Star” : Single-Stellar-Population~ 10 6 Mo –Mass and time resolution is not sufficient –Naïve approximation to the real physics

10. No.10 Our model: chain reaction model SN explosions induce star formation –A SN explosion produce a shell –The shell contains ejecta mass –The shell is the site for next star formation Supernova explosion ISM Mixture of ISM and ejecta Tsujimoto, Shigeyama & Yoshii 1999

11. No.11 Chain reaction model details Gas cloud ~ 10 6 Mo (1)First stars formation 0.04% of the could mass (2)Next stars form in the shell 0.8% of the shell mass (3) Repeated Star formation

12. No.12 Further details of our model Star formation rates by this process Gas mass, stellar mass etc. evolve similarly

13. No.13 CD evolution with CR SF model What we newly have are multiple stellar population star particles!!

14. No.14 Results (1) Initial model : selected from our catalog –Seems to become a disk galaxy (ID 143) N sph ~ N dark ~ 66000 (M sph ~ 10 6 Mo) Evolve upto t = 0.9 Gyr (z~5.5) Chemical evolution of Fe & O –SN explosions heat up the gas particle –Break up when the reaction stops namely separation of “star particle” Resulted in effectively better resolution in mass and time.

15. No.15 Results (2) Obtained metallicity distribution function New model Old model

16. No.16 Results (3) proto-galaxies at z~5.5 R~2.6 kpc D 6.1x10 9 Mo G 3.1x10 9 Mo S 8.1x10 8 Mo R~1.9 kpc D 2.2x10 9 Mo G 1.4x10 9 Mo S 2.6x10 8 Mo R~2.7 kpc D 7.4x10 9 Mo G 3.2x10 9 Mo S 7.0x10 8 Mo

17. No.17 Summary Introducing sub-grid physics (chain reaction model) in our chemical and dynamical SPH code. Better time resolution in CE. Our new model shows better star formation history in the early universe. Future : we will have precise galaxy evolution models with the detailed chemical and kinematical information.