1. Galactic archaeology Rodrigo Ibata Observatoire de Strasbourg

2. age in Gyr mass fraction Abadi, Navarro, Steinmetz & Eke 2003 Fine structure of simulated galaxies thin disk thick disk spheroid

3. The big questions ● Where are/are there missing satellites? ● Are dark matter profiles universal? ● What is the fine distribution of dark matter? ● How did the galaxy build up? ● What was the role of accretion in the formation of the halo, disk, bulge? ● What was the detailed chemical enrichment history?

4. Uniqueness of the MW & Local Group ● Kinematic surveys of 1000s of stars possible ● dynamics of fine structure ● Detailed chemistry ● (chemical tagging of stars?) ● Age-dating of stellar populations

5. Halo structure: streams! J. Bullock

6. Halo streams Majewski et al. 1994

7. Majewski et al. (2003)

8. SDSS colour-selected stars Newberg et al. (2001) also SDSS RRLyraes Ivezic et al. Quest RRLyraes Vivas et al.

9. Substructure in the disk: The Monoceros ring SDSS: Newberg et al. (2002) then Yanny et al. (2003), Ibata et al. (2003), Crane et al. (2003), Rocha- Pinto et al. (2004), Frinchaboy et al. (2004), Peñarrubia et al. (2005) 120°<l<240° |b|<30°, both hemispheres 15 < D GC < 20 kpc almost circular orbit σ vr ~ 20-30 km/s several globular and open clusters coincide with orbit ➙ Accretion stream?

10. An accretion into the disk? ● Heliocentric distance: – TRGB: 7.2 ± 0.3 kpc ● 4-10 Gyr population ● σ=12km/s (Martin et al 2004, 2005, Bellazzini et al. 2005) Outer galaxy in Red Clump stars

11. Canis Major TriAnd Monoceros Ring G. Lewis

12. Blue RGB Red RGB 125 kpc 95 kpc c.f. Andromeda... Outer disk substructure Qualitatively consistent with predictions (e.g. Abadi et al. 2003)

13. Missing satellites? Klypin et al. (1999) Moore et al. (2000) Bullock et al. (2000) Somerville (2001) Stoehr et al. (2002) Kravtsov et al. (2004) Moore et al. 2000

14. New M31 satellites: Metal-poor Neighbors within 8” And III Neighbors within 2” CFHT/MegaCam (Martin et al. 2006 in prep)

15. Neighbors within 12” Neighbors within 8” New M31 satellites: Metal-rich

16. How can we detect completely dark structures? By the heating of globular cluster streams! No dark lumpslumpy DM halo Ibata, Lewis, Irwin, Quinn (2002)

17. existence proof: Pal5 Pal5 : Odenkirchen et al (2001) Dehnen, simulation

18. GAIA ● ~1 billion stars surveyed to V~20 ● proper motions: 10μas at V=15 ● velocities for 10 8 stars (2- 10km/s) to V=17 ● ~10% accuracy parallaxes to 10kpc ● However, no chemical “finger- printing”

19. Chemical tagging...

20. Venn et al. 2004

21. Conclusions ● Studies of nearby galaxies are needed to test cosmological predictions on low-mass scales – dark matter distribution (cusps) – existence of dark satellites – detailed formation history of galaxies ● GAIA will revolutionise this field, but will lack detailed chemical information, as well as accurate radial velocities ● Chemistry (e.g., from ARGOS or WFMOS surveys) may prove to be key additional info to unravel the mess left after all the merging