oltre l'orizzonte cosmologico

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)

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


But also distance in time: 14 Gyrs agoR=14 Gly

Transparentuniverse

Opaqueuniverse

R=14

Glyseveral Gly

T=30

00K

here, now


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.


time

size of the horizon



So a region as large asthe horizon when the CMB is released ….

380000 y


time

size of the horizon



… has never beencausally connectedbefore

380000 y


time

size of the horizon



… 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


time

size of the horizon


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


10-36 s

normal

evolution

Infla

tion:

expo

nent

ial

expa

nsio

n

time

size of the horizon


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




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




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

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).