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Two-part talk • Observed properties of dark matter: a progress update on dynamical studies of dwarf spheroidal galaxies • The European Extremely Large Telescope (in brief..) Update on the European Extremely Large Telescope Gerry Gilmore Chair, Steering Committee Chair, OPTICON ELT Design Study – Contract No 011863 A technology development programme funded by the European Community under its Framework Programme 6 Science case overview Three priority themes : Exo planets Galaxy Formation Frontiers of Physics Direct detection Indirect detection Circumstellar disks First galaxies Stellar populations Physics of galaxies Cosmological parameters Fundamental parameters Black Holes Radial velocity measurements of the nAnd system Butler et al (1999) • Direct imaging detection • Indirect detection (radial velocity) – lower mass planets: e.g. earth-like planets around solar type stars – Large collecting area (requires high spectral resolution) • Stellar disks – Detection of gaps where planets are forming – requires high dynamic range (103-105) – Spectroscopy to probe dynamics and chemistry (dust, gas & ices, organic materials…) Simulations of formation of gas giant planets via fragmentation of protoplanetary disks (Meyer et al 2004) Resolved Stellar populations Aparicio and Gallert (2004) • Measuring age & chemical composition of individual stars • quantify star formation and assembly histories of a galaxy • Map dark matter – (i) Colour-magnitude diagram (photometry) • A ~40m can reach RGB stars for representative galaxies in Virgo/Fornax at ~17Mpc – (ii) Spectroscopic chemical abundances & kinematics • High resolution (diffraction-limited) • Large collecting area M87 in the Virgo cluster (Gendler) Galaxy FormationThe first galaxies • Redshift ~ 6-7 galaxies have been found • Evidence for higher redshift galaxies: – Old stellar populations, SMBH already seen at z~6 – Universe is ionised by something! • • • • Find earlier galaxies by imaging: JWST? ELT imager? Need ELT for continuum spectroscopy (z and physical properties) Large collecting area (faint galaxies) HST images of z~5 galaxies (Bremer & Lehnert 2005) Large Field of View Frontiers of Physics • Dark Matter – Probe via galaxy dynamics • Dark Energy – Type Ia SNe spectroscopy at hi-z – Direct measurement of expansion – [e.g. CODEX, R~150,000] • Variation of fundamental parameters • Black Holes Artist’s concept of an AGN (GLAST/NASA) – angular resolution of ELT probes “sphere of influence” Keck observations of Q1422+231 (Sargent & Rauch) E-ELT Current status • Technical review of general design work late 2005 • Specific designs under study for next review late 2006 • Apertures in range 30m-60m considered, 30-40m likely: driven by schedule to match JWST and ALMA; cost and technology • Major science/technology meeting, 11/2006 (Marseille) • Then progress to detailed design • • • • • Cost ~1G$/euro Schedule: operation ~2016: the second set of Great Observatories ESO Council resolution: We will do it, and not be late Two similar projects, status and timetables in US Presentation of major 2015+ projects, and funding agency overviews, next week @ Prague, IAU GA (Special Session 1) Real why: more photons and resolution = more science! Some observed properties of Dark Matter: a progress report on a dynamical study of the nearby dSph’s Gerry Gilmore IoA Cambridge Mark Wilkinson, Jan Kleyna, Wyn Evans, Justin Read, Andreas Koch, Rosie Wyse, Mike Irwin, Eva Grebel,,…. Data from: VLT, Keck, Gemini, AAT, WHT, INT, eso2.2… The early context • The ``standard’’ value for local DM at the Sun is 0.3GeV/cc, all in a `halo’ component • (cf pdg.lbl.gov: Eidelman etal 2004) • • • • the original work, and origin of this value, is the first analysis to include a full 3-D gravitational potential, parametric modelling, and a direct determination of both the relevant density scale length and kinematic (pressure) gradients from data, allowing full DF modelling for the first time: Kuijken & Gilmore 1989 (MN 239 571, 605, 651), 1991 (ApJ 367 L9); 1989 Gilmore, Wyse & Kuijken (ARAA 27 555) Cf Bienayme etal 2006 A&A 446 933 for a recent study Dark halos are `predicted’ down to sub-earth masses; but… Neither the local disk, nor star clusters, have DM: Given the absence of a ~100pc local enhancement, what is the smallest scale on which DM is concentrated? New data: UP TO 600 *s/GAL Note very low outer-most dispersions in Sextans, Draco, UMi: not yet understood Expected dispersion if no DM: <1km/s Leo I dSph modelling • 1) Use Jeans’ eqn: simple, and robust: also • 2) Multi-component DF models developed (see Wilkinson etal MN 330 778 2002 for details) • Construct parameterised equilibrium dynamical models – vary halo shape, and mass, stellar velocity anisotropy • Predict line of sight kinematics: convolve with observational effects (errors, binaries, sampling…) • Compare with individual data to find best-fit model • OTHER COMPLEMENTARY WORK: • • • Deep HST studies to show stellar M/L `normal’, [ie agrees with Kroupa, Tout, Gilmore local IMF: -- Wyse etal 2002 New Astr 7 395 for UMi] Galactic tides, feedback, etc modelled (eg Read etal 2006 MN 366 429) NOTE many earlier studies used scaled tidally-limited star-cluster (King-) models: these are invalid for extended low-density systems. Breaking the degeneracy – first steps Cold subsystems imply shallow density profiles: NOT as CDM prediction Can we break the anisotropy-mass degeneracy? Distribution Function Models Alternative gravity theories? Dark matter systematics: the 2005 state of play Only 8 galaxies, factor 40 in luminosity….. Systematic properties of DM –I --minimum mass, scale, dispersion? 2006: extend dynamic range by 2 mags Red line: constant mass DM halo, 7 M~4x10 M apparent lower mass boundary Some data are old, central M/L only Now a factor of 200+ in luminosity, 3000+ in M/L Figure from astroph-0602186 Systematic properties of DM –I --minimum mass, length, dispersion? New Boo dwarf data under analysis Observed properties of UMa ``predicted’’ Relation now extends from 40X to 500X in L, from 3 to 3000 in M/L 5 new dSph discovered this year, under study ------------- Exclusion? Globular star clusters, no DM Systematic properties of DM: cores, maximum central density? Survival of cold local structures in UMi – plausibly an evolved star cluster -- requires cored mass distribution Consistent with cored halos: 15GeV/cc Jeans’ eqn mass profiles: total masses 3—8x10^7 Msun Unreliable method at large radius better models underway UMa Fornax Leo I LEAST LUMINOUS MORE LUMINOUS Central density ranking is the inverse rank order to CDM prediction MOND fails New dSph – and debris – being discovered now: test predictions! Systematic properties of DM -II cores, maximum central density? Jeans’ eqn mass profiles: Total masses 3—8x10^7 Msun Unreliable method at large radius Consistent with cored halos: 15GeV/cc Survival of cold local structures in UMi – plausibly an evolved star cluster -- requires cored mass distribution Kleyna etal 2003 [UMi] Kleyna etal 2004 [Sext] Central density ranking is the inverse rank order to CDM prediction UMa Fornax Leo I LEAST LUMINOUS MORE LUMINOUS Distribution Functions Exo-planets • How common are systems like ours? • How do planetary systems form? • To date many planets have been detected indirectly • Direct detection: – Mass, radius, temperature, composition – ELT will provide large samples of mature giant planets in reflected light – Earth-like planets may be within reach • Large collecting area (faint planets) • Large diameter: very high spatial resolution and contrast ~109 Young Giant (5MJ) Exo-planet observed with VLT/NACO (Chauvin et al 2004) Anisotropic Plummer Models dark matter on small scales A vast increase in precise stellar kinematic data allows more sophisticated derivation of mass profiles in the dSph- the smallest galaxies. UMa – discovered 2005 and Boo (2006) – extends to M/L ~ 500-3000!! 4 more found last week… All are consistent with: Central mass cores, not cusps Central mass density ≤20GeV/cc Dispersion ~6-9km/s Scale length ~few x100pc 7 DM minimum mass? ~5x10 M We have new dSph under study (today), to extend the sample further, and see if these numbers are really significant MOND fails The Local Group:detailed test Locally, >90% halo stars are old: recent mergers? The Local Group:detailed test small scales: least clear, Are the predictions reliable? Non-Standard Models Draco vs MOND Mond M/L is still 19…… Are there other unmodelled effects: time-dependent dynamics? Umi: direct HST star counts Wyse etal, luminosity function for Umi is like M92, M15 at low masses. High mass indirect limit from chemical evolution. Orbit, Tidal radius Draco light is *not* tidally limited High-mass, high-redshift IMF Element ratio modelling limits IMF slope dSph Stellar IMF Deep direct star counts (Wyse etal) Element ratio limits at high mass Deep ISO photometry (GG + Unavane) All imply an invariant IMF Stellar M/L=2-4 dSph satellite galaxies: what, why? • Lowest stellar mass galaxies known • In CDM test regime: eg famous sub-structure problem • (ie, >1000 predicted, ~10 found) • Have high M/L (Aaronson 1983) – 3 stars in Draco to deduce M/L=30 1-D velocity dispersion high • 1990 Pryor & Kormendy showed that extended dark halos were consistent with available data • 1997 Mateo: first extended dispersion profile –Fornax • 1998 Mateo noted M/L vs L may imply min DM mass. • 2006: extended dispersion profiles available for Draco, UMi, Leo I, Leo II, Fornax, Scl, Carina, …1-D for UMa, AndII, AndIX with very many high-precision data – up to >500 stars/galaxy [new ones to come – complete sample] • Kleyna etal 2000,2002,2003,2004, 2005, 2006;Tolstoy etal 2004, 2006; Munoz etal 2005; Walker etal 2005; Chapman etal 2005; Wilkinson etal 2004, 2006, Koch etal 06a, 06b