Transcript Some observed properties of Dark Matter: a progress report on an

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!
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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
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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)
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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:
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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
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Red line: constant mass
DM halo,
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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
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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
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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
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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
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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
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Draco light is *not* tidally limited
High-mass, high-redshift IMF
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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
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(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