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Seminario del Prof. Paolo de Bernardis11 Marzo 2010Aula A Dipartimento di Fisicaore 13.15
Citation preview
Oltre l’ orizzonte cosmologico
Paolo de BernardisDipartimento di Fisica
Università di Roma La Sapienza
A pranzo con la fisica - NIPS LabDipartimento di Fisica Università di Perugia
11/03/2010
L’ orizzonte in cosmologia
• L’ orizzonte delle particelle è la superficie che ci separa da quanto non possiamo osservare, perché la luce partita oltre l’orizzonte non è ancora arrivata fino a noi. Le particelle che si trovano oltre l’ orizzonte non sono ancora in contatto causale con noi. Esiste se l’ universo ha un’età finita.
• Esistono però altri orizzonti, di tipo fisico, più vicini di quello delle particelle, che dipendono dai dettagli della propagazione della luce nell’ universo.
Il redshift• Negli anni ’20 Carl Wirtz, Edwin Hubble ed altri, analizzarono la luce proveniente da galassie distanti, e notarono che piu’una galassia e’ distante, piu’ le lunghezze d’ onda della sua luce sonoallungate (spostamento verso il rosso, redshift).•Questo dato empirico viene interpretato come una prova dell’ espansione dell’universo.
Lunghezza d’ onda λ (nm)
Ca II H I
Mg I Na I
laboratorio
Galassia vicina
Galassia lontana
Galassia molto lontana
Percorrendo distanze cosmologiche, la luce cambia colore• La relativita’ generale di Einstein prevede
che, in un universo in espansione, le lunghezze d’onda λ dei fotoni si allunghino esattamente quanto le altre lunghezze.
• Piu’ distante e’ una galassia, piu’ e’ lungo il cammino che la luce deve percorrere, piu’lungo e’ il tempo che impiega, maggiore e’l’ espansione dell’ universo dal momento dell’ emissione a quello dalla ricezione, e piu’ la lunghezza d’ onda viene allungata.
to
t1
t2
• Se vogliamo arrivare a osservare l’ orizzonte, dobbiamo osservare piùlontano possibile.
• La luce che è partita da regioni di universo cosìremote, avrà allungato moltissimo le sue lunghezze d’ onda, diventando infrarossa, o microonde, o radioonde …
• Quindi richiede telescopi e rivelatori speciali per essere osservata.
• L’ orizzonte a cui si arriva, però, è di tipo fisico. • Infatti l’ espansione dell’ universo comporta un suo
raffreddamento. Osservando lontano riceveremo luce che è stata emessa quando l’ universo era piùcaldo di oggi.
• Se guardiamo abbastanza lontano, arriveremo ad osservare epoche in cui l’ universo era caldo come o più della superficie del sole.
• E quindi era ionizzato. In quell’ epoca i fotoni non potevano propagarsi su linee rette, ma su spezzate venendo continuamente diffusi dagli elettroni liberi del mezzo ionizzato.
• L’ universo primordiale è opaco, come opaco è l’interno di una stella.
Orizzonte fisico• In un universo in espansione, dominato dalla
radiazione, si può calcolare accuratamente il tempo necessario per passare dal Big Bang (densità e temperatura infinite) fino alla temperatura in cui elettroni e protoni possono combinarsi in atomi (ricombinazione dell’ idrogeno).
• La temperatura a cui avviene la ricombinazione è circa 3000K, e il tempo necessario per arrivarci è di 380000 anni.
• Quindi per i primi 380000 anni della sua evoluzione l’ universo è ionizzato e opaco.
Orizzonte fisico• Osservando sempre più lontano,
potremo vedere solo finchè l’ universo ètrasparente. Cioè fino all’ epoca della ricombinazione.
• Possiamo quindi osservare entro un orizzonte che è una superficie sferica, centrata sulla nostra posizione, al di làdella quale l’ universo è opaco a causa delle diffusioni (scattering) contro gli elettroni liberi subite dai fotoni.
• Si chiama superficie di ultimo scatteringed è il nostro orizzonte fisico.
Composizione della luce che viene dal sole (spettro)Lunghezza d’ onda (micron)
Inte
nsità
lum
inos
a W
/m2 /s
r/cm
-1)
Radiazione Termica, Spettro di Corpo Nero
0K 5K
Strong evidence for a hot early phase of the Universe
Thermal spectrum ….
… and accurate isotropy
3K
CosmicMicrowaveBackground
Orizzonte fisico• Nel seguito:
–L’ osservazione della superficie di ultimo scattering. • Come si fa• Quali sono i risultati• Orizzonti causali impressi nell’ orizzonte
fisico• Conseguenze per la cosmologia e la
fisica fondamentale–Come andare oltre.
How to detect CMB photons
• E(γCMB) of the order of 1 meV• Frequency: 15-600 GHz• Detection methods:
– Coherent (antenna + amplifier)– Thermal (bolometers)– Direct (Cooper pairs in KIDs)
• Space (atmospheric opacity)
How to detect CMB photons
• E(γCMB) of the order of 1 meV• Frequency: 15-600 GHz• Detection methods:
– Coherent (antenna + amplifier)– Thermal (bolometers)– Direct (Cooper pairs in KIDs)
• Space (atmospheric opacity)
Cryogenic Bolometers• The CMB spectrum is a continuum and bolometers are wide band
detectors. That’s why they are so sensitive.
filter(frequencyselective)
FeedHorn(angle selective)
IntegratingcavityRadiation
Absorber (ΔT)
Thermometer(Ge thermistor (ΔR)at low T)
IncomingPhotons (ΔB)
• Fundamental noise sources are Johnson noise in the thermistor(<ΔV2> = 4kTRΔf), temperature fluctuations in the thermistor((<ΔW2> = 4kGT2Δf), background radiation noise (Tbkg
5) needto reduce the temperature of the detector and the radiativebackground.
Load resistor
ΔV
• Johnson noise in the thermistor
• Temperature noise
• Photon noise
• Total NEP (fundamental):
Cryogenic Bolometers
kTRdf
Vd J 42
=Δ
( )22
22
24
fCGGkT
dfWd
eff
effT
π+=
Δ
( )( ) dxeex
hcTk
dfWd
x
xBGPh
∫ −
+−=
Δ2
4
32
552
114 εε
dfWd
dfWd
dfVd
NEP PhTJ222
22 1 Δ
+Δ
+Δ
ℜ=
Again, needof low
temperatureand low
background
Q
Circa 1970
Circa 1980
Spider-Web Bolometers
Absorber
Thermistor
Built by JPL Signal wire
2 mm
•The absorber is micromachined as a web of metallized Si3N4 wires, 2 μm thick, with 0.1 mm pitch.
•This is a good absorber formm-wave photons and features a very low cross section for cosmic rays. Also, the heat capacity isreduced by a large factorwith respect to the solidabsorber.
•NEP ~ 2 10-17 W/Hz0.5 isachieved @0.3K
•150μKCMB in 1 s
•Mauskopf et al. Appl.Opt. 36, 765-771, (1997)
1900 1920 1940 1960 1980 2000 2020 2040 2060
102
107
1012
1017
Langley's bolometerGolay Cell
Golay Cell
Boyle and Rodgers bolometer
F.J.Low's cryogenic bolometer
Composite bolometer
Composite bolometer at 0.3K
Spider web bolometer at 0.3KSpider web bolometer at 0.1K
1year
1day
1 hour
1 second
Development of thermal detectors for far IR and mm-waves tim
e re
quire
d to
mak
e a
mea
sure
men
t (se
cond
s)
year
Photon noise limit for the CMB
How to detect CMB photons
• E(γCMB) of the order of 1 meV• Frequency: 15-600 GHz• Detection methods:
– Coherent (antenna + amplifier)– Thermal (bolometers)– Direct (Cooper pairs in KIDs)
• Space (atmospheric opacity)
COBE-FIRAS• COBE-FIRAS was a
cryogenic Martin-Puplett Fourier-TransformSpectrometer withcomposite bolometers. It wasplaced in a 400 km orbit.
• A zero instrumentcomparing the specificsky brightness to the brightness of a cryogenic Blackbody
( ) ( )[ ] [ ]{ } σπσσσσ dxrtSSCxI REFSKYSKY 4cos1)()(0
+−= ∫∞
( ) ( )[ ] [ ]{ } σπσσσσ dxrtSSCxI REFCALCAL 4cos1)()(0
+−= ∫∞
MPI(Martin PuplettInterferometer)
Beamsplitter = wire gridpolarizer
Differentialinstrument
FIRAS• The FIRAS guys were able to change the temperature of
the internal blackbody until the interferograms were null. • This is a null measurement, which is much more
sensitive than an absolute one: (one can boost the gain of the instrument without saturating it !).
• This means that the difference between the spectrum of the sky and the spectrum of a blackbody is zero, i.e. the spectrum of the sky is a blackbody with that temperature.
• This also means that the internal blackbody is a realblackbody: it is unlikely that the sky can have the samedeviation from the Planck law characteristic of the source built in the lab.
σ (cm-1) wavenumber
• The spectrum
KTec
hTB
CMB
x
725.21
2),(3
2
=−
=νν
mmTBTB 06.1),(),( max =⇒= λλνλν
GHzkThx
CMBCMB 56
νν≅=
)31.5(159
82.23
1
1maxmax
maxmaxmax
−
−
==
⇒=⇒=−
cmGHz
xxe x
σν
WienRJ
• Techniques ?
???160bolometers160
detectorscoherent 160
max
max
max
⇒=≈⇒=>>⇒=<<
GHzGHzGHz
νννννν
WienRJ
COBE-DMR• The DMR instrument aboardof the COBE satellite measured the first map of CMB anisotropy (1992)
• The contrast of the image isvery low, but there are structures, at a level of 10ppm.
• Instrumental noise issignificant in the maps(compare the three differentwavelengths)
• DMR did not have a realtelescope, so the angularresolution was quite coarse(10 o !!)
Galactic Plane
CMB anisotropy
Cosmic Horizons• The very good isotropy of the CMB sky is to
some extent surprising.• The CMB comes from an epoch of 380000 years
after the Big Bang.• So it depicts a region of the universe as it was
380000 years after the Big Bang. • The region we can map, however, is much wider
than 380000 light years. • So it contains subregions which are separated
more than the length light has travelled since the Big Bang. These regions would not be in causalcontact in a static universe.
T=30
00K
here, now
R= distance fromus = 14 Glyrs
But also distance in time: 14 Gyrs agoR & t
Transparentuniverse
Opaqueuniverse
T=30
00K
here, now
R= distance fromus = 14 Glyrs
But also distance in time: 14 Gyrs agoR=14 Gly
Transparentuniverse
Opaqueuniverse
R=14
Glyseveral Gly
T=30
00K
here, now
R= distance fromus = 14 Glyrs
But also distance in time: 14 Gyrs agoR=14 Gly
Transparentuniverse
Opaqueuniverse
R=14
Glyseveral Gly
r = 380 kly
r = 38
0 kly
Cosmic Horizons• We measure the same brightness
(temperature) in all these regions, and thisis surprising, because to attain thermalequilibrium, contact is required ! (through forces, thermal, radiative …).
• We live in an expanding universe. Regionsseparated by more than 380000 light years might have been in causal contact (and thus homogeneized) earlier.
Expansion vs Horizon
time
size of the horizon
size of the considered region
In a Universe made of matter and radiation, the expansion rate decreaseswith time.
Expansion vs Horizon
time
size of the horizon
size of the considered region
In a Universe made of matter and radiation, the expansion rate decreaseswith time.
So a region as large asthe horizon when the CMB is released ….
380000 y
Expansion vs Horizon
time
size of the horizon
size of the considered region
In a Universe made of matter and radiation, the expansion rate decreaseswith time.
… has never beencausally connectedbefore
380000 y
Expansion vs Horizon
time
size of the horizon
size of the considered region
In a Universe made of matter and radiation, the expansion rate decreaseswith time.
… nor has beencausally connected tosurrounding regions
380000 y
Cosmic Horizons• Hence the “Paradox of Horizons” : • We see approximately the same temperature
everywhere in the map of the CMB, but wedo not understand how this has beenobtained in the first 380000 years of the evolution of the universe.
• Was this temperature regulated everywhereab-initio ?
• Are our assumptions about the compositionof the universe wrong, and the universe doesnot decelerate in the first 380000 years ?
Granulazione solare
8 minuti luceQui, ora
Gas incandescente sulla superficie del Sole (5500 K)
Granulazione solare
Mappa di BOOMERanG dell’ Universo Primordiale
8 minuti luce
14 miliardi di anni luce
Qui, ora
Qui, ora
Gas incandescente sulla superficie del Sole (5500 K)
Gas incandescente nell’ universo primordiale (l’universo diventa trasparente a 3000 K)
Flatness Paradox• The expansion of the Universe is regulated by the
Friedmann equation, directly deriving fromEinstein’s equations for a homogeneous and isotropic fluid.
• If the Universe contains only matter and radiation, iteither collapses or dilutes, with a rate depending on the mass-energy density.
• To get an evolution with a mass-energy density of the order of the observed one today, billions of years after the Big Bang, you need to tune it at the beginning very accurately, precisely equal to a critical value.
• How was this fine-tuning achieved ?
a(t)
t
Critical density, 1 ns after the Big Bang
Billion years
Cos
mic
dist
ance
s
Cosmological scalest=380000 y
density fluctuations
Sub-atomic scales
t=10-36sQuantum fluctuations of the field dominating the energy of the universe
Energy scale:1016 GeV
CosmicInflation
Inflation might be the solution
Cosmic Inflation:
A very fast expansionof the universe, drivenby a phase transition in the first split-second
Expansion vs Horizon
time
size of the horizon
size of the considered region
According to the inflationtheory ….
…had been causallyconnected to the surrounding regionsbefore inflation
380000 y
A region as large as the horizon when the CMB isreleased ….
time
size of the horizon
size of the considered region
10-36 s
normal
evolution
Infla
tion:
expo
nent
ial
expa
nsio
n
time
size of the horizon
size of the considered region
10-36 s
Here the horizoncontains all of the universe observabletoday
Infla
tion:
expo
nent
ial
expa
nsio
n
normal
evolution
• Inflation– Provides a physical process to origin density fluctuations– Explains the flatness paradox– Explains the horizons paradox
• Is a predictive theory (a list of > models has been compiled..) – Predicts gaussian density fluctuations– Predicts scale invariant density fluctuations– Predicts Ω=1
• How can we test it ? • We still expect a difference between the physical processes
happening inside the horizon and those relevant outside the horizon.
• So we expect anyway that the scale of the causal horizon isimprinted in the image of the CMB.
• The angular size subtended by the horizons when the CMB isreleased is around 1 degree, if the geometry of space isEuclidean.
• We need sharp images of the CMB, so that we can resolvethe density fuctuations predicted by inflation.
θ
R
d
oo
lyly
aa
Rd 11100
01400000000380000
≈×≈×≈θ
BigB
ang
(T=∞
)
T=30
00K
Here, now
1o
10o
R
COBE resolution
380000 lyrs
R= distancefrom us= 14 Glyrs
high resolution• The images from COBE-DMR were not sharp
enough to resolve cosmic horizons (the angularresolution was 7°).
• After COBE, experimentalists worked hard todevelop higher resolution experiments.
• In addition to testing inflation, we expected high resolution observations to give informationsabout
a) The geometry of spaceb) The physics of the primeval fireball.
a) The angle subteneded by the horizon can bemore or less than 1° if space is curved.
Critical density Universe
Ω>1
Ω<1
High density Universe
Low density Universe
1o
2o
0.5o
hori
zon
Ω=1
14 Gly
LSS
hori
zon
hor i
zon
Ω>1 Ω=1 Ω<1
2o 1o
0.5o
High density Universe Critical density Universe Low density Universel
PS
l
PS
l
PS
200 200 2000 0 0
The quest for high resolution
b) Within a causally connected region, the hot, ionized gas of the primeval fireball issubject to opposite forces: gravity and photon pressure.
• If a density fluctuation is present, “acoustic oscillations” start, depending on the composition of the universe (density of baryons) and on the spectrum of initialdensity fluctuations.
After recombination, density perturbation can grow and create the hierarchy of structureswe see in the nearby Universe.
Before recombination
After recombination T < 3000 KT > 3000 K
overdensity
Due to gravity, Δρ/ρ increases, and so does T
Pressure of photonsincreases, resisting to the compression, and the perturbation bounces back
T is reduced enoughthat gravity wins again
Here photons are not tightlycoupled to matter, and theirpressure is not effective. Perturbations can grow and form Galaxies.
t
t
Density perturbations (Δρ/ρ) were oscillating in the primeval plasma (as a result of the opposite effects of gravity and photon pressure).
• The study of solar oscillationsallows us to study the interior structure of the sun, well belowthe photosphere, because thesewaves depend on the internalstructure of the sun.
• The study of CMB anisotropyallows us to study the universewell behind (well before) the cosmic photosphere (the recombination epoch), becausethe oscillations depend on the composition of the universeand on the initial perturbations.
How to obtain wide, high angularresolution maps of the CMB
• Angular Resolution: Microwave telescope, at relatively high frequencies (θ=λ/D)
• 150GHz: peak of CMB brightness• Low sky noise and high transparency at 150 GHz:
Balloon or Satellite • High sensitivity at 150 GHz: cryogenic bolometers• Multiband for controlling foreground emission
In Italy: ARGO In the USA: MAX, MSAM, …
Statistical samples of the CMB sky (about one hundred directions) in the 90s
How to obtain wide, high angularresolution maps of the CMB
• Angular Resolution: Microwave telescope, at relatively high frequencies (θ=λ/D)
• 150GHz: peak of CMB brightness• Low sky noise and high transparency at 150 GHz:
Balloon or Satellite • High sensitivity at 150 GHz: cryogenic bolometers• Multiband for controlling foreground emission• Sensitivity and sky coverage (size of explored
region): either– Extremely high sensitivity (0.1K) and regular flight
or– High sensitivity (0.3K) and long duration flight
How to obtain wide, high angularresolution maps of the CMB
• Angular Resolution: Microwave telescope, at relatively high frequencies (θ=λ/D)
• 150GHz: peak of CMB brightness• Low sky noise and high transparency at 150 GHz:
Balloon or Satellite • High sensitivity at 150 GHz: cryogenic bolometers• Multiband for controlling foreground emission• Sensitivity and sky coverage (size of explored
region): either– Extremely high sensitivity (0.1K) and regular flight
or– High sensitivity (0.3K) and long duration flight
MAXIMA
BOOMERanG
Universita’ di Roma, La Sapienza:P. de Bernardis, G. De Troia, A. Iacoangeli, S. Masi, A. Melchiorri, L. Nati, F. Nati, F. Piacentini, G. Polenta, S. Ricciardi, P. Santini, M. VenezianiCase Western Reserve University:J. Ruhl, T. Kisner, E. Torbet, T. MontroyCaltech/JPL: A. Lange, J. Bock, W. Jones, V. HristovUniversity of Toronto: B. Netterfield, C. MacTavish, E. Pascale
Cardiff University: P. Ade, P. MauskopfIFAC-CNR: A. BoscaleriINGV: G. Romeo, G. di StefanoIPAC: B. Crill, E. HivonCITA: D. Bond, S. Prunet, D. PogosyanLBNL, UC Berkeley: J. BorrillImperial College: A. Jaffe, C. ContaldiU. Penn.: M. Tegmark, A. de Oliveira-CostaUniversita’ di Roma, Tor Vergata: N. Vittorio, G. de Gasperis, P. Natoli, P. Cabella
BOOMERanG
Sun Shield
Ground Shield
Solar Array
Cryostat and
detectors
Primary Mirror
(1.3m)
Differential GPS Array
Star Camera
the BOOMERanG ballon-borne telescope
Sensitive at 90, 150, 240, 410 GHz
0.3K
1.6K
120 mm
Focal plane assemblyBOOMERanG-LDB Appl.Opt
D D
DD
D DD
preamps
3He fridge
D = location of detectors
4o on the sky
MultiBandPhotometers
(150,240,410)150 150
90 90
• The instrument is flownabove the Earthatmosphere, at an altitudeof 37 km, by means of a stratospheric balloon.
• Long duration flights (LDB, 1-3 weeks) are performadby NASA-NSBF over Antarctica
• BOOMERanG has been flownLDB two times:
• From Dec.28, 1998 toJan.8, 1999, for CMB anisotropy measurements
• In 2003, from Jan.6 toJan.20, for CMB polarizationmeasurements (B2K).
9/Jan/1999
BOOMERanG• 1998:
BOOMERanG mapped the temperature fluctuations of the CMB at sub-horizonscales (<1O).
• The signalwas wellabove the noise:
2 indep. det.at 150 GHz
• 1998: BOOMERanG mapped the temperature fluctuations of the CMB at sub-horizonscales (<1O).
• The rmssignal has the CMB spectrum and does not fitany spectrumof foregroundemission.
Ω>1 Ω=1 Ω<1
2o 1o
0.5o
High density Universe Critical density Universe Low density Universel
PS
l
PS
l
PS
200 200 2000 0 0
Full power spectrummeasurementfromBOOMERanG (2002)
-Geometry of the universefrom location of first peak
-Signature of inflation fromamplitudes of 3 peaks and general slope
Size of sound horizon
timeBig-bang recombination Power Spectrum
mul
tipol
e22
045
0
1st peak
2nd peak
LSS
380000 ly
In the primeval plasma, photons/baryons density perturbations start to oscillate only when the sound horizonbecomes larger than their linear size . Small wavelength perturbations oscillate faster than large ones.
R
R
C
C
C
C
1st dip
2nd dip
Th e
an g
le su
bten
ded
depe
n ds o
n th
e ge
ome t
ryof
spa c
e
size of perturbation(wavelength/2)
300000 y0 y
v vv
v v
v v
v
Temperature Angular spectrum varies with Ωtot , Ωb , Ωc, Λ, τ, h, ns, …
We can measure cosmological parameters with CMB !
“The perfect universe”
• Data consistent with flat Universe
• Baryon fraction agrees with BBN
• With supernovae or LSS => Λ term
NormalMatter
4%
Dark Matter22%
Dark Energy
74%
Radiation< 0.3%
Did Inflation really happen ?• We do not know. Inflation has not been
proven yet. It is, however, a mechanism ableto produce primordial fluctuations with the rightcharacteristics.
• Four of the basic predictions of inflation havebeen proven: – existence of super-horizon fluctuations– gaussianity of the fluctuations– flatness of the universe– scale invariance of the density perturbations
• One more remains to be proved: the stochasticbackground of gravitational waves producedduring the inflation phase.
• CMB can help in this – see below.
Last scattering surface
CMB polarization• CMB radiation is Thomson scattered at recombination.• If the local distribution of incoming radiation in the
rest frame of the electron has a quadrupole moment, the scattered radiation acquires some degree of linearpolarization.
-
-
+
-
+x
y
--
+
-
+
x
y
-x
y
-10ppm +10ppm
= e- at last scattering
If inflation reallyhappened…
• It stretched geometry of space to nearly Euclidean
• It produced a nearly scale invariant spectrum of density fluctuations
• It produced a stochasticbackground of gravitationalwaves.
?
OK
OK
• If inflation really happened:It stretched geometry of space tonearly EuclideanIt produced a nearly scale invariantspectrum of gaussian density fluctuationsIt produced a stochastic background of gravitational waves: Primordial G.W.The background is so faint that evenLISA will not be able to measure it.
• Tensor perturbations also produce quadrupole anisotropy. They generate irrotational (E-modes) and rotational(B-modes) components in the CMB polarization field.
• Since B-modes are not produced by scalar fluctuations, they represent a signature of inflation.
Quadrupole from P.G.W.
E-modes
B-modes
• The amplitude of this effect is very small, butdepends on the Energy scale of inflation. In fact the amplitude of tensor modes normalized to the scalar ones is:
• and
• There are theoretical arguments to expect that the energy scale of inflation is close to the scale of GUT i.e. around 1016 GeV.
• The current upper limit on anisotropy at large scalesgives T/S<0.5 (at 2σ)
• A competing effect is lensing of E-modes, which isimportant at large multipoles.
GeV107.3 16
4/14/1
2
24/1
×≅⎟⎟
⎠
⎞⎜⎜⎝
⎛≡⎟
⎠⎞
⎜⎝⎛ V
CC
ST
Scalar
GW Inflation potential
B-modes from P.G.W.
⎥⎥⎦
⎤
⎢⎢⎣
⎡
×≅
+GeV102
1.02
)1(16
4/1
maxVKcB μ
π l
ll
06/01/2003
PSB devices & feed optics (Caltech + JPL)
PSB Pair
[Masi et al. 2005]
145 GHz T map
(Masi et al., 2005)
the deepestCMB map ever
• Detection of anisotropy signals all the way up to l=1500
• Time and detector jacknife tests OK• Systematic effects negligible wrt noise & cosmic variance
B03 TT Power Spectrum
Jones et al. 2005
La mappa dell’ universo primordiale con sovrapposta la polarizzazioneRealizzata dal gruppo di Cosmologia di Tor Vergata (Genn. 2005)
19/20
TE Power Spectrum
Piacentini et al. 2005
• Smaller signal, but detection evident (3.5σ)
• NA and IT results consistent
• Error bars dominated by cosmic variance
• Time and detectors jacknife OK, i.e. systematics negligible
• Data consistent with TT best fit model
EE Power Spectrum
Montroy et al. 2005
• Signal extremely small, but detection evident for EE (non zero at 4.8σ).
• No detection for BB nor for EB
• Time and detectors jacknifeOK, i.e. systematicsnegligible
• Data consistent with TT best fit model
• Error bars dominated by detector noise.
Montroy et al. 2005
WMAP (2002)
Wilkinson Microwave Anisotropy Probe
WMAP in L2 : sun, earth, moon are allwell behind the solar shield.
WMAPHinshaw et al. 2006astro-ph/0603451
BOOMERanGMasi et al. 2005astro-ph/0507509
1oDetailed Views of the Recombination Epoch(z=1088, 13.7 Gyrs ago)
Hinshaw et al. 20062006
Processed bycausal effects like
Acoustic oscillations
Unperturbed
Quantum fluctuationsin the earlyUniverse IN
FLA
TIO
NP(
k)=A
kn
k
horizon horizon
l
l ( l +
1) c
l
horizon
Scal
essm
alle
rtha
nho
rizon
Scal
esla
r ger
tha n
horiz
o n
tBig-Bang10-36s 300000 yrs0
plasma neutral
Power spectrum of perturbations
Power spectrumof CMB temperaturefluctuations
Paradigm of CMB anisotropies
Radiation pressurefrom photonsresists gravitationalcompression
Inflation
(ΔT/T) = (Δρ/ρ) /3 + (Δφ/c2)/3– (v/c)•n
Gaussian,adiabatic(density)
Nucleosynthesis3 min
Recombination
Hinshaw et al. 20062006
Need for high angularresolution
< 10’
Cosmological ParametersAssume an adiabatic inflationary model, and compare with same weak prior on 0.5<h<0.9
WMAP(100% of the sky, <1% gain
calibration, <1% beam, multipole coverage 2-700)
Bennett et al. 2003
• Ωο =1.02+0.02• ns = 0.99+0.04 *• Ωbh2 =0.022+0.001• Ωmh2 =0.14+0.02• T = 13.7+0.2 Gyr• τrec= 0.166+0.076
BOOMERanG(4% of the sky, 10% gain
calibration, 10% beam, multipole coverage 50-1000)
Ruhl et al. astro-ph/0212229
• Ωο = 1.03+0.05• ns = 1.02+0.07• Ωbh2 =0.023+0.003• Ωmh2 =0.14+0.04 • T=14.5+1.5 Gyr• τrec= ?
Planck is a veryambitiousexperiment.
It carries a complex CMB experiment (the state of the art, a few years ago) all the way to L2,
improving the sensitivity wrtWMAP by at least a factor 10,
extending the frequencycoveragetowards high frequencies by a factor about 10
2009
PLANCKESA’s mission to map the Cosmic Microwave Background
Image of the whole sky at wavelengths near the intensity peak of the CMB radiation, with• high instrument sensitivity (ΔT/T∼10-6)
• high resolution (≈5 arcmin)
• wide frequency coverage (25 GHz-950 GHz)
• high control of systematics
•Sensitivity to polarization
Launch: 2009; payload module: 2 instruments + telescope• Low Frequency Instrument (LFI, uses HEMTs)
• High Frequency Instrument (HFI, uses bolometers)
• Telescope: primary (1.50x1.89 m ellipsoid)
CMB
Galaxy
CMB
Galaxy
CMB
Galaxy
Two Instruments: Low Frequency (LFI) and High Frequency (HFI)
Spider Web and PSB Bolometers
• Ultra-sensitive Technology• Tested on BOOMERanG (Piacentini et al.
2002, Crill et al. 2004, Masi et al. 2006) forbolometers, filters, horns, scan at 0.3K and on Archeops at 0.1K (Benoit et al. 2004).
• Crucial role of balloon missions to getimportant science results, but also tovalidate satellite technology.
Measured performance of Planck HFI bolometers (0.1K)(Holmes et al., Appl. Optics, 47, 5997, 2008)
=Photonnoiselimit
Multi-moded
Planck-HerschelLaunchMay 14, 200915:12 CEST
Telescopio fuori asse, diametro specchio principale 1.8 m
Ecliptic plane1 o/day
Boresight(85o from spin axis)
Field of viewrotates at 1 rpm
E
M
L2
Observing strategyThe payload will work from L2, toavoid the emission of the Earth, of the Moon, of the Sun
LaunchMay 14th, 2009
CruiseMay-June 2009
Calibrations, Scanstart July 2009
Main beamFar side lobesSpectral responseTime responseOptical polarisationThermo-optical coupling, bckgndLinearityAbsolute responseDetection noiseCrosstalkDetection chain caractNumerical compressionCryo chain setupCompatibilityScanningSolar AA
sub-system
HFI focal plane
(IAS, CSL)in-flig
ht
LIGH, BEAMLIGH, BEAM
LFER, SPINLIGH, POLC01TO, 16TO, 4KTO4KTOLIGHRW72, SPIN, NOISXTLKQECn, IVCF, IBTU, PHTUCPSE, CPVA4KTU,16TU, 01TUXTRA, NOISACMS [1.7arcmin]SUNI [50%]
HFI Verification / Calibration Plan
3 months after launch● The launch was flawless and the transfer to final orbit
was completed on 1 July● All parts of the satellite survived launch and it is fully
functional● Coldest temperature (0.1 K) was reached on 3 July. The
thermal behavior (static and dynamic) is as predicted from the ground.
● The instruments have been fully tuned and are in stable operations since 30 July
● All planned initial tests and measurements have been completed on 13 August
● Planck is now transitioning into routine operational mode
Preview of data from the first-light survey (2 weeks of stable operation)
The sky explored by Planck so far (First Light Survey, 2 weeks)
The sky explored by Planck so far (First Light Survey, 2 weeks)
Galactic Plane
The sky explored by Planck in the First Light Survey, first 2 weeks
High Galactic Latitude (CMB)
After Planck
• Planck will do many things but will not do:– Accurate measurement of B-Modes
(gravitational waves from inflation) through polarization (unless we are very lucky …)
– Measurements at high angular resolution– Deep surveys of clusters and superclusters of
galaxies for SZ effect
PolarizationHigh ResolutionAnisotropy λ-spectrum
of the CMB and its anisotropy
•Damping tail & param.s
• SZ & Clusters
• nature of dark matter
• neutrino physics•…..
• SZ distortions• Early Metals• Recombination lines• CII• …
• Inflation
• Reionization
• Magnetic fields
• …..
precisionCMB
measurements
After Planck: CMB arrays• Once we get to the photon noise limit, the only
way to improve the measurement is to improve the mapping speed, i.e. to produce large detector arrays.
• The most important characteristic of future CMB detectors, in addition to be CMB noise limited, is the possibility to replicate detectors in largearrays at a reasonable cost.
• Suitable detection methods:– TES bolometers arrays– Direct detection and KIDs arrays
Bolometer Arrays• Once bolometers reach BLIP
conditions (CMB BLIP), the mapping speed can only beincreased by creating largebolometer arrays.
• BOLOCAM and MAMBO are examples of large arrayswith hybrid components (Si wafer + Ge sensors)
• Techniques to build fullylitographed arrays for the CMB are being developed.
• TES offer the naturalsensors. (A. Lee, D. Benford, A. Golding, F. Gatti …)
Bolocam Wafer (CSO)
MAMBO (MPIfR for IRAM)
NowNow
APEX 12m telescopeAtacama (ALMA site)
295 bolometers LABOCA (345 GHz) Bonn
330 bolometers APEX-SZ (150 GHz) Berkeley
QP
CP
T<Tc
Attenuation ≈ 0dB
Effect of a signal transmitted through the feed line past the resonator:
amplitudephase
Which are the effects of incoming radiation?
hν >2DE
n′CP< nCP Zs changes
• nQP
• nCP
Rs
Lkin
Claudia Giordano
SCN-CN coax
2xDC block2xDC block2x10dB atten
1xDC block1xDC block1x10dB atten
KID
300K
30K
2K
300mK
SCN-CN coax
SS-SS coax
amplifiers
KIDs testbench: cryogenic system and RF circuit
Cryostat modifiedto have RF ports
3x10dB atten
bias generator and acquisition data system
VNA : slower, easier, can give informationon the sanity of the whole circuit. Ideal for the first runs.
IQ mixers: faster, essential to measurenoise, QP lifetime... Need fast acquisition system
36mm
Array of 81 LKID built by the RIC (INFN gruppo V) collaboration(Dip. Fisica La Sapienza, FBK Trento, Dip. Fis. Perugia
JulyJuly 11stst, 2009, 2009First First largelarge balloonballoon
FromFrom SvalbardsSvalbards
B-Pol(www.b-pol.org)
• European proposal recentlysubmitted to ESA (CosmicVision).
• ESA encourages the development of technology and resubmission for next round
• Detector Arrays developmentactivities (KIDs in Rome, TES in Oxford, Genova etc.)
• A balloon-borne payload beingdeveloped with ASI (B-B-Pol).
Sensitivity and frequency coverage: the focal plane• Baseline technology: TES bolometers arrays
Sub-K, 600 mmCorrugated feedhornsfor polarization purity and beam symmetry
.. Ancora moltissimo da fare
Vedi anche: PdB - Osservare l’ Universo - Il Mulino (da Aprile)
Per saperne di più…
• Steven Weinberg “I primi tre minuti”, Oscar Mondadori (Milano, 1986).
• Italo Mazzitelli “Tutti gli universi possibili e altri ancora”, Liguori Editore (Napoli, 2002),
• Paolo de Bernardis “Osservare l’ Universo”, Il Mulino (Bologna, da Aprile 2010).