1. LOGO The Chemical and Color Evolution of M33 2008.12 Reporter: Jun Yin (Shao) Supervisor: Jinliang Hou (Shao)

2. Contents Observations 1 Models 2 Results & Forming History 3 Summary 4

3. Observation  Sc II-III, i=56, D=840 kpc  M tot =5~8×10 9 M ⊙  r d,tot =2.4kpc, r d,* ~1.4kpc  no merger whole gas & SFR abundance SB, color

4. Observation  H 2,tot =0.2×10 9 M ⊙, HI tot =2.2×10 9 M ⊙  r d,H2 =2.5kpc, r d,tot =7.8kpc whole gas & SFR abundance SB, color

5. Observation whole gas & SFR abundance SB, color

6. Observation Munoz-Mateos et al. (2007) M FUV = -16.63 (GALEX) M K = -21.78 (2MASS) whole gas & SFR abundance SB, color

7. Chemical & Color Evolution Model Star Formation Rate Gas Infall Rate Outflow…… mass SFR Z, MDF color …… stellar evolution theoryInitial conditions

8. Model  f out ~b·Ψ, Z out =Z(t)  Ψ~(Σ gas ) 1.4 r -1  f in ~t·exp(-t/τ), Z in =0  t d =a·r Gyr  M tot =7×10 9 M ⊙, r d,tot =2.2kpc  Σ tot (r)=230*exp(-r/r d,tot ) Total SFR Infall rate Outflow

9. Results & Forming History  Does M33 form quickly ?  if τsmall  infall quick  gas ， SFR low  stellar disk big  abundance high, steep  SB dark, color red NO τ= r+5 Gyr

10. Results & Forming History  Does infall delay at outer part ?  if t d large  infall late  gas fraction high  stellar disk small  abundance low, steep  color blue, steep Not necessary t d = 0 Gyr -0.015 -0.022 -0.034 μ r = 23.2 mag arcsec -2 G kpc = -0.016

11. Results & Forming History  Does gas flow out ?  if b large  outflow large  gas, SFR, star do not change much  abundance low, flat  color a little flatter YES ! b=1.0 -0.020 -0.017 -0.015 μ r = 23.2 mag arcsec -2 G kpc = -0.016

12. Results & Forming History  MDF & evolution of some global variables in our best model  τ= r+5 Gyr  t d = 0 Gyr  b= 1.0

13. Summary  M33 should be forming though slow accretion process, i.e. longer infall time scale.  The whole disk should form simutaneously, no obvious infall delay at outer disk.  Outflow is not negligible because of its low metallicity.  The M33 should obey similar SF law with our Galaxy.

14. LOGO