KIAA/PKU -- IoA workshop “Near Field Cosmology” Beijing, Dec 1-5, 2008

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 Astronomical Mansion Shanghai Astronomical Observatory, CAS • Star Clusters and the Structure of Galaxies

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

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. Content • 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

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 • For the average properties of a galaxies, KS law is OK • 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 thick disk thin disk bulge We would like to understand how our Galaxy came to looklike 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 Total disk SFR MW M31 Yin, Hou, Chang et al. 2009

20. 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) [O/H]gradient from young objects Scaled gradient MWD:－0.161 －0.093 M31 :－0.094 －0.017 dex / kpc

21. Scaled profiles MW MW Gas SFR M31 M31 Gas fraction

22. Model comparisons between M31 and Milky Way disks

23. Purpose of the chemical evolution studyfor 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 Phenomenological Model / Semi-Analytical Model 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

25. Unified One Component Model • Disk forms by gas infall from outer dark halo • Infall is inside-out • SFR: • modified KS Law (SFR prop to v/r)

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

30. Summary : M31 disk properties • Current star formation properties are atypical in the M31 disk. • Disk formation be affected by interactions • 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 : • PN (Maciel et al. 2003, 2005, 2006, 2007) and • Open Clusters (LAMOST Survey, CHEN Li’s talk, this workshop)

32. Comparison among MW, M31 and M33

33. Thanks

35. Observed difference between M31 and Milky Way galaxies

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

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

38. Disk scale length M31 distance: 785kpc Band Observed scale length ( kpc ) M31 the Milky Way U 7.7 B 6.6 4.0-5.0 V 6.0 R 5.5 2.3-2.8 I 5.7 K 4.8 L 6.1 Note: SDSS average rd = 4.75kpc (Pizagno et al. 2006)

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

40. Observation: which galaxy is a “typical” spiral? Statistical • M31 : metal-rich halo • MWG: metal-poor halo • 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?

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 • MDF (Metallicity Distribution Function) disk and halo • [O/Fe] versus [Fe/H] from metal poor to metal rich • SFR at present time

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

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

44. Star formation: Kennicutt law Halo Disk

45. Chemical evolution Gas of an elementi 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 Phenomenological Model • Two time scales: • h depends on the halo formation mechanism • d as a function of radius, disk formation Halo Disk delayed by tdelay

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