Galactic archaeology

1. Galactic archaeology Rodrigo Ibata Observatoire de Strasbourg

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

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 < DGC < 20 kpc • almost circular orbit • σvr ~ 20-30 km/s • several globular and open clusters coincide with orbit ➙ Accretion stream?

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

11. Canis Major TriAnd Monoceros Ring G. Lewis

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

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” Neighbors within 2” And III CFHT/MegaCam (Martin et al. 2006 in prep)

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

16. How can we detect completely dark structures? By the heating of globular cluster streams! No dark lumps lumpy 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 108 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