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The Local Group

The Local Group. THE LOCAL GROUP. 35 - 40 members M31, and its satellites (red) Milky Way, and its satellites (blue) Isolated dwarfs (blue). Mass Length Time. Stellar Archaeology and Galaxy Genesis. DE + DM + VM. Mike Irwin.

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The Local Group

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  1. The Local Group THE LOCAL GROUP 35 - 40 members M31, and its satellites (red) Milky Way, and its satellites (blue) Isolated dwarfs (blue) Mass Length Time

  2. Stellar Archaeology and Galaxy Genesis DE + DM + VM Mike Irwin • LR kinematic and general metallicity measures of main Galactic structures • detailed HR abundances of these to trace chemical development over time • LR analysis of surviving nearby galaxies and streams • exploit synergy with GAIA to break degeneracies

  3. Credit: Matthias Steinmetz

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

  5. Galaxy substructure and satellite accretion 38 30 23 CDM models predict large-scale subtructure in L galaxies like M31 and MW * Bullock & Johnston 2005 300 x 300 kpc

  6. Near-field cosmology - some key questions • where are the missing satellites? • are dark matter profiles universal? • what is the extent nature and spatial distribution of dark matter? • how were the Galaxy and M31 constructed? are they typical disk galaxies? • what was the role of accretion in the formation of the halo, disk, bulge? • what was the detailed chemical enrichment history of the stellar components?

  7. Galactic Science

  8. clusters galaxies Belokurov et al. 2006 AndXV AndXVI single stellar componentsno DM ? mulitple stellar components DM ? missing satellites ?? AndXIV AndXI AndXII AndXIII

  9. Missing satellites & Halo DM lumpiness Pal5 : Odenkirchen et al (2003)

  10. An accretion into the MW 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)

  11. DART Canis-Major and the Monoceros Ring

  12. DART

  13. Galactic Science • chemo-dynamic structure of Galactic components - interface between disk, bulge/bar, halo - ancient dissolved and surviving substructures • fossil record of chemical evolution of stellar pops - chemical signature of ancient accretions - properties of metal-poor popIII stars • evolutionary history of stellar components - IMF, SFH, tagging the chemical development - the role of star clusters • linking the Bulge to the high Z universe • detailed chemo-dynamics of surviving satellites

  14. What do you need - I ? • wide field well calibrated imaging optical -> NIR • north: SDSS ugriz, WFCAM UKIDSS zyJHK • south: Skymapper, VST, CTIO 4m DES, VISTA • all-sky: 2MASS calibration and pathfinder • GAIA: proper motions and parallaxes • large area stellar spectroscopy (million stars) • automate majority of processing and analysis => logg, Teff, vel, [m/H]

  15. What do you need - II ? • large telescope with a wide fov eg. degrees diam • 1000-4000 fibres to exploit target surface density • survey selected regions totalling ~1000 sq deg • larger systematic survey find new structures • LR -> Mgb 4800-5500A and CaT 8150-8850A vels to < 10 km/s; [Fe/H] to 0.1-0.2 dex; limited chemical tagging e.g. [alpha/Fe] ? • synergy with GAIA => LR to ~V=20 => full 6D kinematic phase space information

  16. GA substructure with LAMOST + • dsphs and “dark” satellites eg. UMaI, UmaII ...... • tidal streams eg. GCs; dSphs; orphan streams • open clusters and unbound debris • known halo/disk sub-structures eg. Triang-And-Perseus; Sgr stream; Hercules-Aquila cloud; Arcturus group ....... • outer disk eg. warp -v- Canis Major edge of, outer spiral arm structure

  17. DART LAMOST and GA competition

  18. Summary • large area spectroscopic studies of nearby galaxies are needed to test cosmological predictions on low-mass scales • nature and distribution of dark matter • detailed formation history of galaxies • GAIA will revolutionise this field, but will lack detailed chemical information, as well as accurate radial velocities

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