1. KIAA/PKU -- IoA workshop “Near Field Cosmology” Beijing, Dec 1-5, 2008 Star Formation and Chemical Evolution of the Milky Way and M31 Disks Jinliang HOU In collaboration with : Ruixiang CHANG, Jun YIN, Jian FU, Li CHEN, Shiyin SHEN et al. Center for Galaxy and Cosmology Shanghai Astronomical Observatory, CAS

2. A short introduction of our group Star Clusters and the Structure of Galaxies Astronomical Mansion Shanghai Astronomical Observatory, CAS

3. Research interests of the group Structure and evolution of galaxies ---- from the Milky Way to high z galaxies  Star clusters and the structure of the Milky Way Galaxy  Chemical evolution of the galaxies, high-z galaxies (mainly Damped Lyman Alpha systems)  Structure and dynamics of the nearby galaxies  Large sample analysis of the nearby galaxies (SDSS, Galex, 2MASS, LAMOST et al. )  Galaxy formation and evolution

4. PhD students: 1.YIN Jun 2.LIU Chenzhe 3.SHI Xihen 4.GAO Xinhua 5.Wang Caihong 6.GAN Jinalin (now in Heideberg, MPIA), 7.HAN Xuhui (now in Paris Observatoire) 8.FU Jian (now in Munich, MPA) MS Students ： 1.YU Jinchen 2.WANG Youfen Staff 1.HOU Jinliang 2.CHEN Li 3.SHAO Zhenyi (now in UMASS, USA) 4.CHANG Ruixiang 5.SHEN Shiyin Senior Professors ： 1. ZHAO Junliang 2. FU Chenqqi 3. WANG Jiaji

5. Some international collaborators ： White S.D.M, Kauffmann G. (MPA) Prantzos N. (IAP) Boissier S. (Observatoire de Marseille) Tytler D. (UCSD) Mo Houjun (UMASS) Levshakov S. (Ioffe Institute of Physical Technique) de Grijs R. (U. Sheffield)

6. Some group members

7.  Local SFR Law in the Milky Way disk based on abundance gradient evolution  Observed differences between M31 and MW disks  Model comparisons between M31 and Milky Way disks  Summary Content

8.  Local SFR Law in the Milky Way disk based on abundance gradient evolution

9. Kennicutt Law --- average properties Strong correlation between the average gas mass surface density and SFR density for nearby disk and starburst galaxies (Kennicutt 1998)

10. Two types of correlations The later form implies SFR depends on the angular frequency of the gas in the disk. This suggestion is based on the idea that stars are formed in the galactic disk when the ISM with angular frequency Omega is periodically compressed by the passage of the spiral pattern.

11. Applications of Kennicutt SFR law When the Kennicutt law is applied in the detailed studies of galaxy formation and evolution, there are several formulism that often adopted by the modelers : SFR 

12. The evolution of abundance gradient along the Milky Way disk Infall SF Law Model A, B Model C

13. Fu, Hou, Chang et al. 2009

14. Adoption of SFR Law for the chemical evolution model of spiral galaxies 1.For the average properties of a galaxies, KS law is OK 2.For local properties, SFR could be local dependent, a simple description is the introducing of angular velocity (Silk 1997, Kennicutt 1998 )

15.  Observed differences between M31 and MWG

16. M31 and MWG have similar mass and morphology

17. Components in the Milky Way Galaxy dark halo stellar halo thin disk thick disk bulge We would like to understand how our Galaxy came to look like this.

18. The Milky Way, typical or not?  It is always regarded that the MWG is the typical spiral in the universe, especially at its mass range.  Is this true?  How about M31 galaxy, it is a spiral that is comparable with MWG in the Local Group, and now it is possible to have detailed observations.

19. Disk Profiles Yin, Hou, Chang et al. 2009 Total disk SFR MW M31

20. [O/H] gradient from young objects － 0.017 dex / kpc Two gradients reported: Steep: － 0.07 dex / kpc (Rudolph et al. 2006 ) Flat: － 0.04 dex/kpc (Deharveng et al. 2000 Dalfon and Cunha 2004) Scaled gradient MWD: － 0.161 － 0.093 M31 : － 0.094

21. Scaled profiles MW M31 MW M31 GasSFR Gas fraction

22.  Model comparisons between M31 and Milky Way disks

23. Purpose of the chemical evolution study for The Milky Way and M31 disks Using the same model Find common features Find which properties are galaxy dependent M31 and MWG, which one is typical ?

24. Model classification Disk only : One component: Disk (Hou et al.) Two components: Thick Disk + Thin Disk (Chang et al.) Disk+Halo: Two components: Disk +Halo Three components: Thick Disk + Thin Disk + Halo Disk+Halo+Bulge: Three components: Bulge+Disk+Halo Semi-Analytical ModelPhenomenological Model /

25. Unified One Component Model 1.Disk forms by gas infall from outer dark halo 2.Infall is inside-out 3.SFR: modified KS Law (SFR prop to v/r) M31 diskMW disk M tot (Ms) 7  10 10 3.5  10 10 r d (kpc) ( R band)5.52.3 V flat (km/s)220226

26. Radial Profiles as constrains Gas profile SFR profile Abundance gradient  Do the similar chemical evolution models reproduce the global properties for the Milky Way and M31 disks ?

27. SFR

28. M31 gas and SFR in disk  Observed of gas and SFR profiles are abnormal when compared with Kennicutt law.  Gas and SFR must be modified by some interaction

29. Block et al. (Nature 2006) Observed Simulation M32 Two rings structure

30. Summary : M31 disk properties 1.Current star formation properties are atypical in the M31 disk.  Disk formation be affected by interactions 2.Has low SFR in disk  shorter time scale for the infall.  contradicts the longer infall time scale for halo.

31. Problems  Chemical evolution model cannot reproduce the outer profiles of gas surface density and SFR profiles at the same time  The observed abundance gradient along the Milky Way disk still not consistent  The evolution of gradients is very important. Two tracers : 1.PN (Maciel et al. 2003, 2005, 2006, 2007) and 2.Open Clusters (LAMOST Survey, CHEN Li’s talk, this workshop)

32. Comparison among MW, M31 and M33 MWDM31 diskM33 disk (Yin Jun’s talk ) Infall Timescale Quiet 7Gyr Interaction 7Gyr Slow Accretion 15Gyr SFRLocal dependent Modulated by events Local dependent OutflowNo Yes Abundance Gradient Steep/flat ?FlatSteep

33. Thanks

35. Observed difference between M31 and Milky Way galaxies

36. Hammer et al. 2007 Halo properties Metal - Velocity Tully-Fish Relation SDSS: 1047 edge-on spirals

37. Mouhcine et al. 2005 Halo properties Metallicity – luminosity relation X X -- M33

38. Disk scale length Band Observed scale length ( kpc ) M31 the Milky Way U7.7 B6.6 4.0-5.0 V6.0 R5.52.3-2.8 I5.7 K4.8 L6.1 Note: SDSS average r d = 4.75kpc (Pizagno et al. 2006) M31 distance: 785kpc

39. AM prop to r d V rot (Mo et al. 1998) Disk specific angular momentum (AM) Hammer et al. 2007 MW is about a factor of 2 less than nearby spirals

40. Observation: which galaxy is a “typical” spiral? Statistical  Zibetti et al. (2004) from SDSS survey: 1000 edge-on disc galaxies, metal-rich halo is more common.  Harris & Harris (2001) NGC5128 similar to M31 halo Metal-rich seems more common  How halo forms ? Why metal-rich ?  Does observed halo really halo? M31 : metal-rich halo MWG: metal-poor halo

41. Observational constrains in the solar neighborhood Find a set of parameters that can best reproduce some observational constrains in the solar neighborhood. Observables of the Milky Way Galaxy 1.MDF (Metallicity Distribution Function) disk and halo 2.[O/Fe] versus [Fe/H] from metal poor to metal rich 3.SFR at present time

42. Physics of the model : Gas infall and star formation proceeds in each ring Physical process Disk profile Gas SFR Abundance gradients other global quantities Rings independent Solar neighborhood Gas fraction Abundance ratio [O/Fe] ～ [Fe/H] G-dwarf metallicity etc.

43. Infall Model Two time scales: –  h depends on the halo formation mechanism –  d as a function of radius, disk formation Halo Disk delayed by t delay Phenomenological Model

44. Star formation: Kennicutt law Halo Disk

45. Chemical evolution Gas of an element i Gas depletion Low mass SNIa IMS star SNII Halo and disk

46. K dwarf Halo

47. Halo : Disk : Disk and halo surface density profile Disk : exponential Halo: modified Hubble law

48. Metallicity Distribution in the MW Disk and Halo

49. Infall Model Two time scales: –  h depends on the halo formation mechanism –  d as a function of radius, disk formation Halo Disk delayed by t delay Phenomenological Model

50. [O/H] gradient from young objects in the Milky Way Disk － 0.07 dex / kpc Rudolph et al. 2006

51. Halo Globular Clusters Number distribution  Double peak Number:  M31: 700  MW: 162

52. [Fe/H] gradient from Open Clusters in the Milky Way disk All Open Clusters ： age mixed － 0.063dex/kpc Chen, Hou, Wang (2003)

53. Summary – 2 : possible correlation between halo Z and Mstar Model predicts more massive stellar halo in M31, about 6 to 9 times than that of MW halo. Massive halo has higher metallicity. Bekki, Harris & Harris (2003) simulation : Stellar halo comes from the outer part of the progenitor discs when the bulge is formed by a major merger of two spirals.  Correlation between halo metallicity and bulge mass

54. What we can do next for M31 ? Similar model, at present, we only concentrate on disk Need to include halo also, a lot of observations are available for the halo, especially in the field of globular clusters. To add the color evolution, this is important to constrain the model, is it possible to consistent between chemical and color ? To solve the problem of low gas density in the outer disk, introduce new assumption ? –Higher outer disk SFE ? –Wind in the outer disk ? –Interaction ?