Title: PowerPoint Presentation Globular Cluster Ages and Dark Energy
1Projects
First come first served..
- A new neutral majorana fermion, k, that interacts
only with neutrinos (all species with equal
strength) via exchange of a new U(1) gauge boson
of mass 350 GeV is rumored to have been observed
in accelerator expts. It is apparently stable,
but its mass and coupling strength are not yet
known. How can cosmology help? - A new axion-like particle with mass 10-3 eV and
fAMpl is posited, but its cosmological and
astrophysical implications need to be explored. - A new unstable heavy fermion of mass 500 GeV, but
with gravitational coupling strength to all light
particles is claimed to exist. Is this
consistent with existing cosmological
constraints? - New observations are made that suggest that Fermi
constant, and the gravitational constant are both
changing with time, as t-.005. Discuss the
implications for Big Bang Nucleosynthesis. - A supernova located 10 kpc away from us goes off,
and 3,000 events are observed in
Super-Kamiokande. The burst lasts 20 seconds,
and 1300 electron neutrino events are observed,
100 muon neutrino events, and 600 tau neutrino
events.. Give the implications for neutrino
physics and cosmology. - A remarkable new laboratory experiment measures
dark energy, and just to embarrass Lawrence
Krauss, they find w -1.2. Give the implications
for cosmology, life, stellar evolution, particle
theory, or whatever..
2Cosmology 566 Class 3Age Constraints, Density
of the Universe
34. Hubble Age.
If the Universe is decelerating t lt H-1
VHd
td/vH-1
For constant velocity
More generally
Problem 3 Show
a
Flat matter dominated
b
Flat rad. dominated
Flat, matter W0 plus Dark energy Wx
c
44. Hubble Age.
Note for a cosmological constant
(greater than H-1 because universe Accelerating!)
Also note
For a flat matter dom. U
While for a cosmological constant dominated
universe the Z dependence is different for z a
few! (ref Ap. J. 480, 466 and Ap.J. 593 (2003)
622)
Thus, limits on H give limits on t! Compare to
other estimates of t to constraint cosmology
54. Hubble Age Absolute Limits
Recall that
astro-ph/0212369
Upper limit on Hubble Age!.
64. Hubble Age Upper Limit Limits on w
WMAP, etc t 13.7 0.4 Gyr (95)
astro-ph/0305556
74. Hubble Age Upper Limit Limits on w
WMAP, etc t 13.7 0.4 Gyr (95)
astro-ph/0305556
84. Hubble Age Upper Limit Limits on w
Including anticorrelation between omega and H
astro-ph/0305556
94. Hubble Age Upper Limit Limits on w
W-1 0.22
104. Hubble Age.cont..
Flat matter dominated
Recall
Flat rad. dominated
Plug in Numbers
H-19.77 h-1 Gyr
Hence for hgt.63 t0 lt 10 Gyr (flat, matter
dominated)
Note for open matter dominated universe
(with W gt0.2) t lt .8 H-1 lt12.4 Gyr for
flat, universe with with Wx 0.7 t 0.96 H-1
lt 14.9 Gyr
(Prove)
11A Lower Limit on the Age of the Universe Dating
Globular Cluster Stars
Theorem tuniverse gt tgalaxy
12- Globular Cluster Ages and Cosmology A Brief
History - Globular Cluster Dating A Primer
- New results abundances and distances
- Constraints on Equation of State
13A Brief History
- 1800 tstars 10,000 yrs
- 1900 tstars 100 Myr
- 1945 tstars 10 Gyr
- 1980s toldest stars 16-20 Gyr
To be compared with Hubble age for a flat
matter dominated universe t 2/3H-1 6.6
(h-1) Gyr
The first modern era evidence for dark energy?
14Stellar Dating
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16Globular Cluster Colour Magnitude Diagram
Main Sequence lifetime L Mstar3 T M/L T M-2
Hydrostatic equilibrium
(An eq. at the basis of most astrophysics)
Mstar
17But..
UNCERTAINTIES!
18Observational Uncertainties!
19Theoretical Uncertainties!
20Theoretical Uncertainties!
21i.e..
22Isochrone Fitting
23Isochrone Fitting
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25Age Determination Techniques
- D Magnitude (TO - HB) -- vertical method
- D Colour (TO - RGB) -- horizontal method
- Isochrone Fitting
26DColour Age Determinations
- Difference in colour between the main sequence
turn-off and the base of the RGB - Used to determine ages of globular clusters
- Well defined observational quantity -- gives
precise relative ages - Difficult to calibrate theoretically as a result
should only be used to determine relative ages of
clusters with similar heavy element abundances - Comparisons between different clusters have found
that all metal-poor clusters (Fe/H lt -1.7) have
the same age, but an age spread of a few Gys
appears among the more metal-rich clusters
27DMagnitude Ages
- Difference in magnitude between the main sequence
turn-off or the SGB and the HB - turn-off/SGB magnitude as a function of age
determined from theoretical isochrones - Absolute magnitude of the HB determined using a
variety of methods - STANDARD CANDLES FIT
- Main sequence fitting to GCs
- White dwarf fitting to GCs
- HB Stars
- Statistical parallax
- RR Lyr stars in the LMC
- Parallax of field HB stars
- Astrometric (GC proper motion dispersion vs.
radial velocity dispersion)
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29HB calibration
- Express HB magnitude calibration in terms of RR
Lyr magnitude typically it has been assumed that
Mv(RR) is a linear function of metallicity - Mv(RR) a Fe/H b
- Slope a affects relative ages for clusters of
different metallicities - Zero-point b affects the absolute ages
- Recent theoretical HB calculations find that the
HB magnitude also depends on the HB type of the
cluster (Demarque et al. 2000) - Observations by Lee Carny (1999) and Clement
and Shelton (1999) have also suggested that
clusters with equal metallicities have different
RR Lyr magnitudes - For now, best to use the DMagnitude method for
clusters with similar HB types
30Absolute GC Ages
- Interested in the oldest clusters -- select a
sample of metal-poor (Fe/H lt -1.6) blue HB
clusters - Minimize theoretical errors by using the best
understood age determination method -- the
absolute magnitude of the main sequence turn-off - Need to know distance (absolute magnitude of the
RR Lyr stars) - Calibrate RR Lyrae magnitude using metal-poor
objects
31Ages of the Oldest Globular Clusters
- Critically examine the age determination processs
and evaluate possible sources of error using a
Monte Carlo simulation, in which the following
variables used to determine the absolute age of
the oldest globular clusters are varied within
their known uncertainties - Abundance of heavy elements, including oxygen
- Nuclear reaction rates
- Opacities
- Mixing length
- Surface boundary conditions
- Diffusion coefficients
- Colour transformation table
- Helium abundance
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34New Analyses
35Oxygen Abundances at Fe/H -1.9
- Assume O/Fe 0.2 to 0.7 (flat distribution)
36Effect of Oxygen Abundance on the Derived Age
37Atomic Diffusion
- Helioseimology clearly shows that diffusion
occurs in the Sun - Fe abundance observations in NGC 6397 show that
diffusion is not occuring in the outer layers of
metal-poor stars - As far as ages are concerned, inhibiting
diffusion in the outer layers of a star is
similar to reducing the diffusion coefficients by
50 - Uncertainty in the diffusion coefficient
calculations estimated to be G30 - For the Monte Carlo, multiply the nominal
diffusion coefficients by 0.2 to 0.8
(flat distribution)
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39High Redshift Deutrium abundances and BBN suggest
YPRIMORDIAL 0.245
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41Use Mv(RR) 0.47 (0.13, -0.10)
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43Absolute Age
44The Minimum Age of the Universe
- Mean age of 17 metal-poor (Fe/H lt -1.6) GC
with blue HBs determined using the set of MC
isochrones and Mv(RR) 0.47 (0.13, -0.10) mag - tGC 12.6 Gyr
- One sided 95 CL lower limit of 10.4 Gyr
- One sided 95 CL upper limit of 16 Gyr
- To determine the age of the universe, one must
add to this age the amount of time which passed
between the big bang and the formation of the
oldest GCs in the Milky Way
45Formation Time of GCs
Lower Limit important -recent studies Lyman a
systems z lt 5 (z lt6) Fortunately age of universe
insensitive to cosmological Uncertainties for Z
gt3-4
Recall
tgc gt 0.8 Gyr
46Constraints on Cosmology
- At the 95 CL, the oldest globular clusters have
an age of 10.4 Gyr, so the age of the universe
- t0 gt 11.2 Gyr (95 CL)
- Hence
- Hoto gt 0.80 (95 CL) (H70)
- Hoto gt 0.92 (68 CL) (H70)
-
- Note Best fit age to 13.4 Gyr
47Now, use equation, for z0 to determine Hubble
age for flat universes with varying equation of
state, and compare to Globular cluster lower limit
Definitive evidence for dark energy if the
Universe is flat!
48H0 70
49H0 63
50Note
- SENSITIVE DEPENDENCE ON H
- NON-TRIVIAL LIMITS ON Wmatter!
- BEST FIT 13.4 Gyr.
- An Wm 0.3, WL 0.7 universe has Hoto 0.96
which implies to 13.2 Gyr for h0.7!
51Comparison to Other Ages
- White dwarf cooling curves determine the age of
the oldest stars in the thin disk to be 9 - 12
Gyr, while my MSTO age for the oldest stars in
the thin disk is 10 Gyr - Deep HST observations found a white dwarf
sequence in M4 by Richer et al. 1997 that the
faintest white dwarfs observed were 9 Gyr
old - Uranium (238) 14.0 2.4 Gyr
- Th and Uraniaum 13.8 4 Gyr
- Observations of detached ecliping double lined
spectroscpic binaries allow one to determine the
mass of the individual stars (Pacyñski 1996,
BC,LMK 2002)
52Age-Mass Relation?
53Preliminary.. Single star.. Uncertainties?
54Preliminary.. Single star.. Uncertainties?
55Recent result
56Direct Parallaxes to Globular Clusters
57Conclusion..Ages
Comparison of WMAP Hubble Age and GC age -A
Flat matter dominated Universe is ruled
out. -(b) Flat with wlt0 component.
Formation of our Galaxy! WMAP 13.7 0.2
Gyr redshift of reionization 17 (200 Myr
aBB) Compare with GC 95 CL lower limit 10.4
implies 3.7 Gyr upper limit on Time to form
MW. 75 likelihood less than 13.5 Gyr old..
Therefore globular clusters formed well after
reionization Hierarchical MODEL!
58II. Density of the Universe
Problem Telescopes measure light, not mass!
Mean (Optical) Luminosity
In galaxies
Clearly a lower limit.. What about the rest?
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60Keplers Discovery
61Newtons Law of Gravity
- Brahe
- Kepler..
- Newton Fma, av2/r, v21/r
62Newtons Law of Gravity
- Brahe
- Kepler..
- Newton Fma, av2/r, v21/r
63Weighing the Sun!!!
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66A little bit of Luck
What if dust component ?1/r2
67If it works. Copy it!
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71Every Galaxy!!!
72Every Galaxy!!!
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76Isothermal Spheres A Cultural Aside
Assume v isotropic, independent of radius, ie
ltv2gt T
Collisionless No interactions
Hydrostatic Equilibrium
Solve as r-gtinfinity
77How Much Dark Matter is out there?
- Local mass estimates i.e. clusters
- global mass estimates
- Large scale structure
- Distance-redshift relation
- Direct measures of geometry