Two-part talk
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Transcript of Two-part talk
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 EuropeanExtremely Large Telescope
Gerry Gilmore
Chair, Steering CommitteeChair, OPTICON
ELT Design Study – Contract No 011863A technology development programme funded by the European Community under its Framework Programme 6
Science case overview
Three priority themes :
Exo planets
Direct detectionIndirect detectionCircumstellar disks
Galaxy Formation
First galaxiesStellar populationsPhysics of galaxies
Frontiers of Physics
Cosmological parameters Fundamental parametersBlack Holes
• 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 proto-planetary disks (Meyer et al 2004)
Radial velocity measurements of theAnd system Butler et al (1999)
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
Resolved Stellar populations
M87 in the Virgo cluster (Gendler)
Galaxy Formation- The 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)• Large Field of View
HST images of z~5 galaxies (Bremer & Lehnert 2005)
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
– angular resolution of ELT probes “sphere of influence”
Artist’s concept of an AGN (GLAST/NASA)
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 GilmoreIoA 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 Leo I
Note very low outer-most dispersionsin Sextans, Draco, UMi: not yet understood
Expected dispersion if no DM: <1km/s
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,
M~4x107M 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 dataunder analysis
Exclusion?
Globular star clusters, no DM
Observed properties of UMa ``predicted’’
Relation now extendsfrom 40X to 500X in L,from 3 to 3000 in M/L
5 new dSph discoveredthis year, under study
Systematic properties of DM:cores, maximum central density?
Leo I
LEAST LUMINOUSLEAST LUMINOUS
MORE LUMINOUSMORE LUMINOUS
15GeV/cc
Jeans’ eqn mass profiles:total masses 3—8x10^7 MsunUnreliable method at large radiusbetter models underway
Consistent with cored halos:
UMa
Survival of cold local structures in UMi – plausibly an evolvedstar cluster -- requirescored mass distribution
Fornax
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 -IIcores, maximum central density?
Leo I
LEAST LUMINOUSLEAST LUMINOUS
MORE LUMINOUSMORE LUMINOUS
15GeV/cc
Jeans’ eqn mass profiles:Total masses 3—8x10^7 MsunUnreliable method at large radius
Consistent with cored halos:
UMaSurvival of cold local structures in UMi – plausibly an evolvedstar cluster -- requirescored mass distribution
Kleyna etal 2003 [UMi]Kleyna etal 2004 [Sext]
Fornax
Central density ranking is the inverse rank order to CDM prediction
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 DM minimum mass? ~5x107M 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 countsWyse etal, luminosity function for Umi is like M92, M15at 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