2. Cosmologia Despues de WMAP. Menu du Jour. Historia del descubrimiento del CMB Fisica del CMB - Radiacion de Cuerpo negro T=2.73 K - Dipolo (Doppler) - Fluctuaciones - Espectro de Potencia Angular 3. Observaciones - COBE y WMAP
DT = 3.358 mK
V_sun w.r.t CMB:
369 km/s towards
l=264o , b=+48o
Motion of the Local Group:
V = 627 km/s towards
l = 276o b= +30o
see QuickTime movie mw in cosmology2
[Visit the website of Wayne Hu: http://background.uchicago.edu/~whu]
Image credit: W. Hu
At any given time before recombination,
the largest l possible for an acoustic
mode is that which the sound speed can
travel in the Hubble time
half a degree.
The acoustic mode that had time to
compress ( heat) the fluid for the
first time at z~1000 should thus have
an angular size of half a degree.
“Frozen” by decoupling, that mode
should appear as a peak at
l = 100/a ~ 200
By analogous logic, the next
acoustic mode should correspond
to an oscillation that had time to
compress and expand once: its
angular scale should thus be half
that of the fundamental mode.
The second mode is a rarefaction
The third mode is one that went
through the cycle:
in one Hubble time; its angular scale
is 1/3 that of the fundamental mode
and it is caught at z~1000 near max
And so on.
The position ( l number) of the peaks of the power spectrum
is strongly dependent on the curvature of space.
The identification of the first acoustic peak indicated that
the Universe is spatially FLAT.
Display curvature2 Quick Time Movie in cosmology2
Varying h between 0.35 and 0.7
h2Wb = 0.0125 is fixed
Varying Wb between 0.01 and 0.10
h = 0.5 is fixed
Increasing the baryon density increases the density
of the coupled photon-baryon fluid, altering the
balance between pressure and gravity in the fuid.
Compression modes (peaks 1 and 3) are enhanced
with respect to rarefaction modes (peak 2).
the relative height of contiguous peaks yields Wb
Credit: Martin White
h2Wb = 0.0125 and h=0.5 are fixed
Time variation of the CMB power spectrum
between a(t)=1/2000 and a(t)=1 (now)
The angle subtended by a given physical size
at last scattering (i.e. a given mode) decreases
as the Universe expands, shifting the peaks to
the right (high l, small angle).
according to WMAP
1. Get good image of galaxy,
measure PA, position slit
2. Pick spectral line,
measure peak l along slit
3. Center kinematically
4. Fold about kinematical
5. Correct for disk
6. You now have a
Pick a parametric
model and fit it.
Inner scale length
“Direct” slope is –7.6
“Inverse” slope is –7.8
SCI : cluster Sc sample
…which is similar to the explicit
theory-derived dependencea = 3
I band, 24 clusters, 782 galaxies
[Giovanelli et al. 1997]
[WhereL a (rot. vel.) ]
A TF template relation is derived
independently on the value of Ho .
It can be derived for, or averaged
over, a large number of galaxies,
regions or environments.
When calibrators are included,
the Hubble constant can be gauged
over the volume sampled by the
From a selected sample of Cepheid
Giovanelli et al. (1997) obtain
H_not = 69+/-6 (km/s)/Mpc
averaged over a volume of
cz = 9500 km/s radius.
The HST key-project team
[Sakai et al 2000] gets 71+/-4+/-7
Zehavi et al. (1999) : Local Hubble bubble within cz = 7500 km/s ?
Giovanelli et al. (1999) :No local Hubble Bubble to cz ~ 15000 km/s
Given a field of density fluctuations d(r) , an
observer at r=0 will have a peculiar velocity:
where W is W_mass
The contribution to by fluctuations
in the shell , asymptotically
tends to zero as
The cumulative by all fluctuations
Within R thus exhibits the behavior :
If the observer is the LG,
the asymptotic matches the CMB dipole
SFI [Haynes et al 2000a,b]
Peculiar Velocities in the
LG reference frame
SFI [Haynes et al 2000a,b]
Peculiar Velocities in the CMB
The reflex motion of the LG,
w.r.t. field galaxies in shells of
progressively increasing radius,
convergence with the CMB dipole,
both in amplitude and direction,
near cz ~ 5000 km/s.
[Giovanelli et al. 1998]
[Giovanelli et al. 2000]
Convergence to the CMB dipole is confirmed
by the LG motion w.r.t.
a set of 79 clusters out to
cz ~ 20,000 km/s
[Giovanelli et al 1999 ;
Dale et al. 1999]