MATTEO VIEL STRUCTURE FORMATION INAF and INFN Trieste SISSA - 3 rd March and 7 th March 2011.
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Transcript of MATTEO VIEL STRUCTURE FORMATION INAF and INFN Trieste SISSA - 3 rd March and 7 th March 2011.
MATTEO VIEL
STRUCTURE FORMATION
INAF and INFN Trieste
SISSA - 3rd March and 7th March 2011
OUTLINE: LECTURES
1. Structure formation: tools and the high redshift universe
2. The dark ages and the universe at 21cm
3. IGM cosmology at z=2=6
4. IGM astrophysics at z=2-6
5. Low redshift: gas and galaxies
6. Cosmological probes LCDM scenario
OUTLINE: LECTURE 2
Physics of 21cm transition in the high redshift universe
LOFAR cosmological perspectives
SKA cosmological perspectives
Review: Furlanetto, Oh, Briggs (2006)
Cosmic history
30-240 MHz window z = 5-46 about 90 % of the age of the universe
?
Main characters: DM haloes +…..
Mo & White 2002
LOFAR
Physics at 21cm - I
Three processes determine Ts:1- absorption of CMB photons timescale of eq 3x105 yrs/1+z2- collisions with other hydrogen atoms, free electrons and protons C10-C01 Important in dense gas
3- scattering of UV photons P10-P01
Line profile
xc coupling coefficient for collisionsx coupling coeffictiont for UV scattering – WF eff.
Spontaneous emission 10-15 s
Ts = spin temperature definition Almost all astrophysical processeshave Ts >> T*
Physics at 21cm - II
Differential brightness temperature of spin against CMB
If T s >> T it saturates to a given value but if T s < T can be arbitrary large
Physics at 21cm - III
Heating per baryon by i-th process: compton,X-ray heating, Lyman-alpha
Compton heating drives Tk-TTill recombination time exceeds expansion time-scaleThen matter and radiation decouple
T K ~ 1+z
T K ~ (1+z)2
Expansion term
T ~ 1+z coupled with CMB radiationT ~ (1+z)2 matter expanding adiabatically
Physics at 21cm: Atoms and photons - IV
z dec = Compton heating becomes inefficient and T K < T for the first time ~ 150 (b h2/0.023)2/5 This is the thermal decoupling redshift
Z coll = Density below coll At this point T s T and the signal vanishes. This is produced by collisions and x c = 1
z h = redshift at which the IGM is heated above T
z c = redshift at which x=1 and T s and T K are coupled
z r = reionization redshift
ATOMIC PHYSICS
LUMINOUS SOURCES
Physics at 21cm: Emission or absorption - V
Absorption or emission: crucial input is of course ionization fraction
Semi-analytical model for reionization (see review or Crociani et al. 08)
Ionization fraction
Ionization efficiency
Star formation / escape fraction / number of ionizing photons per baryon
Collapse fraction from PS
Recombination coefficient / Clumping factor
During reionization heat input is
How would the universe at z~12 look like? LCDM DARK ENERGY
Tsujikawa 08
How would the universe at z~12 look like - II? LCDM LCDM + different physics for galaxy formation
Galactic winds + multiphaseStar formation criterion
How would the universe at z~12 look like - III? LCDM DARK ENERGY
Gas overdensity
Neutral hydrogen fraction
SKY AND FREQUENCY INFORMATION
Radio sky much brighterthan CMB
Probability distribution functions
Number of haloes
z = 12
Pdf and correlation function
Tozzi et al. 2001Ciardi & Madau 2003
High redshift pdf reflects density in the linear regimeLow redshift signal is dominated by ionization fraction
Lya photons suceed in decoupling the CMB and spin temperature at very high redshift
1 arcmin ~ 2 com Mpc/h at z=12
IGM tomography at high redshift: expansion
Observable: brightness temperature fluctuations in SPACE and FREQUENCY :
(x) = [T b (x) – T b] / T b
Expanding to linear order:
= bxxpecvel
Baryons/neutral fraction/Ly- coupling/Kinetic gas temperature
Furlanetto, Oh, Briggs (2006)
z c = 18 and z h = 14 and z r = 7
Coefficients are complicated….. And are intrinsically gastrophsyical….
IGM tomography at high-z: Cosmological parameters
Mc Quinn et al. 2006
1- density fluctuations dominate the signal xi0 TCMB<<TS
2- bubbles are present and contaminate the signal but P6 and P4 are significant3- at very large scales where ionization fluctuations are unimportant
Noise + sample variance: SKA black, MWA blue, LOFAR red
Thin line is signal for xi<<1 and TS >>TCMB
IGM tomography at high-z: growth factors
Signal isotropy is broken by: - different scaling of transverse and parallel distance ALCOCK-PACZYINSKI (AP) TEST - redshift space distortions
= 2 f b+
isotropic
P(k) = 4 P(k) + 2 2 P (k)iso + P(k) iso iso
The power is boosted and most importantly power of density perturbations can be isolated
w(z) = w0 + w a (1+z)
IGM tomography at high redshift: powerspectra
1 – boosting factor 2- since the power depend on the angle one can evaluate the power at different values of the angle and isolate the different contributions
Matter
McQuinn et al. 2006
IGM tomography at high redshift: AP and NG
AP test: Nusser (2005) MNRAS, 364, 743
1/H
D n
orm
aliz
ed
to s
tan
dard
mod
el
Non gaussianity: Pillepich, Porciani, Matarrese (2006)
Cooray (2006)
subarcminute angular resolution needed !!
Factor 10 better than the CMB
(x)= L (x) + f NL(2
L(x)-<2
L(x)>)
Few arcsec resolution - LOFAR extended?
But small f sky (LOFAR-120 fsky=0.5)
z ~ 50
z ~ 20
Mhz
real space
Eke & 2dFGRS 2003
Peculiar velocities Peculiar velocities manifest themselves in manifest themselves in galaxy surveys as galaxy surveys as redshift-space distortionsredshift-space distortions
Peculiar velocities
redshift space
Line of sight to observer
Peculiar velocities manifest themselves in galaxy surveys as redshift-space distortions
Moreover, measuring separations parallel and perpendicular to the l.o.s. requires assuming a cosmological model that may be different from the true one
Peculiar velocities-II
The same argument holds true for the 21cm brightness temperature maps.
Measuring the 2-point correlation function in the direction parallel and perpendicular to the l.o.s. on can constrain:
- The growth rate of density fluctuations from redshift distortions.
-The expansion rate of the universe (and the cosmological parameters andM) from geometry-induced distortions (the Alcock-Paczynski effect).
Line of sight to observer
T21
(i)
T21 (j)
Mesinger & Furlanetto 07Peculiar velocities-III
Pair separation perpend. to line-of-sight rp (Mpc/h)
Redshift-space Temperature-Temperature correlation Redshift-space Temperature-Temperature correlation functionfunction
1420GHz
c
1 z
rp H(z)DA (z)
Pair
separa
tion
alo
ng lin
e-o
f-si
gh
t (
h-1 M
pc)
Figures by
Marco Pierleoni
s
rp
No redshift distortions
Model:Redshift: z=8m=0.25, =0.75f(m)= (m)0.55/b=0.5b=2100 km/s
Pair separation perpend. to line-of-sight rp (Mpc/h)
Redshift-space Temperature-Temperature correlation Redshift-space Temperature-Temperature correlation functionfunction
1420GHz
c
1 z
rp H(z)DA (z)
Pair
separa
tion
alo
ng lin
e-o
f-si
gh
t (
h-1 M
pc)
Linear redshift distortions only.Flattening proportional to growth rate of density fluctuations.
Pair separation perpend. to line-of-sight rp (h-1 Mpc)
Redshift-space Temperature-Temperature correlation Redshift-space Temperature-Temperature correlation functionfunction
1420GHz
c
1 z
rp H(z)DA (z)
Pair
separa
tion
alo
ng lin
e-o
f-si
gh
t (
h-1 M
pc)
Redshift distortions generating small-scale “spindle” due to nonlinear motions withinvirialized regions (100 km/s)
Pair separation perpend. to line-of-sight rp (h-1 Mpc)
Redshift-space Temperature-Temperature correlation Redshift-space Temperature-Temperature correlation functionfunction
1420GHz
c
1 z
rp H(z)DA (z)
Pair
separa
tion
alo
ng lin
e-o
f-si
gh
t (
h-1 M
pc)
Geometry distortions(AP effect) from having assumedm=1.00,=0.00
Pair separation perpend. to line-of-sight rp (h-1 Mpc)
Redshift-space Temperature-Temperature correlation Redshift-space Temperature-Temperature correlation function function
1420GHz
c
1 z
rp H(z)DA (z)
Pair
separa
tion
alo
ng lin
e-o
f-si
gh
t (
h-1 M
pc)
All distortionsincluded
MEASURING DENSITY FLUCTUATIONS
Could be doable over a significant fraction of the cosmic time finding deviations from LCDMand measuring the dark energy at early stages (if any)
Subarcminute resolution will be important (extended LOFAR)
--Measuring geometrical distortions in the iso-correlation Measuring geometrical distortions in the iso-correlation contours of the 21 cm maps around the epoch of re-contours of the 21 cm maps around the epoch of re-ionization allows to discriminate among competing dark ionization allows to discriminate among competing dark energy models.energy models.
-Measuring dynamical distortions in the iso-correlation -Measuring dynamical distortions in the iso-correlation contours of the 21 cm maps around the epoch of re-contours of the 21 cm maps around the epoch of re-ionization allows to break the degeneracy between Dark ionization allows to break the degeneracy between Dark Energy and Modified Gravity models and test the Energy and Modified Gravity models and test the gravitational instability picture.gravitational instability picture.
ALCOCK-PACZINSKI TEST
However, the task is observationally challenging, unless density fluctuations dominate over fluctuations in the neutral hydrogen fraction
A significant improvement can be obtained by cross-correlating the 21 cm mapwith deep galaxy redshift surveys. Results will depend on the relative bias ofHI and galaxy which, however, can be determined self-consistently from the data
SKA and galaxies -I
Blake, Abdalla, Bridle, Rawlings, 2004, aph-0409278Rawlings et al., 2004, aph-0409479Seo & Eisenstein 2003, ApJ, 598, 720Abdalla & Rawlings, 2005, MNRAS, 360, 27
SKA P(k) estimates not correlated small k-window function good
to probe features in the P(k) V SKA = 500 V 2dF
New regimes:Big volumes (small k) and high z (large k not affected by non linearities)
Survey requirements big fraction of the sky
- HI emission line survey - 109 (fsky/0.5) HI galaxies up to z=1.5 - probably the smallest masses probed
will be 5x109 Msun - Shown is a model for which Mbar ~ AM DM
WMAP PLANCK
0.5-1.4 GHz survey with large FOV
SKA and dark energy -II
Ultimate goal is again to constrain the dark energy properties at high z
Note that due to intrinsic degeneracies (w-m) the CMB alone (PLANCK) cannot probe w better than 0.1
SKA and weak lensing -III
Cosmic shear survey: high image quality (shape measurement), high source surface density, wide area
Advantages: point spread function for radio telescopes is stable, 1010 (fsky/0.5) sources good resolution 0.05 arcsec at 1.4 GHz, 30 nJy in a 4 hrs pointing
Disadvantage: unknown radio source population
The goal is to estimate the lensing power spectrum and derive cosmological parameters
SHEAR ALONE z=10,15SHEAR ALONE z=10,30,100
Blake et al. 2004 Metcalf & White 2006
F sky=0.5200 sources/sqarcmin
SUMMARY
SKA will probably be the most powerful dark energy probe and its accurate measurement of the P(k) will offer insights on the nature of dark matter; sinergies with particle physics
(inflation and elementary particles) will be fundamental
Effects of dark energy through ISW effectPhysics of inflationAdiabatic/isocurvature fluctuationsGaussianityFeatures in the P(k)Geometry/topology of the Universe
LOFAR extended with large field of view will probably we able to map
HI at z=12 (120 Mhz) with arcsec resolution allowing first studies of the topics above
SUMMARY
1 – Atomic physics of 21 cm and implication for astrophysics (light) and cosmology (matter) in the high redshift universe
2 – cosmological tests (AP test) and the power spectrum
3 – Reionization highlights in standard and non-standard structure formation scenarios (dark energy, non gaussianities etc.)