MATTEO VIEL STRUCTURE FORMATION INAF and INFN Trieste SISSA - 3 rd March and 7 th 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= 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 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 3x10 5 yrs/1+z 2- collisions with other hydrogen atoms, free electrons and protons C 10 -C 01 Important in dense gas 3- scattering of UV photons P 10 -P 01 Line profile x c coupling coefficient for collisions x  coupling coeffictiont for UV scattering – WF eff. Spontaneous emission s T s = spin temperature definition Almost all astrophysical processes have T s >> 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-  T  Till recombination time exceeds expansion time-scale Then matter and radiation decouple T K ~ 1+z T K ~ (1+z) 2 Expansion term T ~ 1+z coupled with CMB radiation T ~ (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 h 2 /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 + multiphase Star 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 brighter than CMB

Probability distribution functions

Number of haloes z = 12

Pdf and correlation function Tozzi et al Ciardi & Madau 2003 High redshift pdf reflects density in the linear regime Low 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:  =  b  x   x          pecvel 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 density fluctuations dominate the signal xi  0 T CMB <<T S 2- bubbles are present and contaminate the signal but P  6 and P  4 are significant 3- at very large scales where ionization fluctuations are unimportant Noise + sample variance: SKA black, MWA blue, LOFAR red Thin line is signal for x i >T CMB

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) = w 0 + 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/HD normalized to standard model 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)- ) 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 manifest themselves in galaxy surveys as redshift-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    and  M ) from geometry-induced distortions (the Alcock-Paczynski effect). Line of sight to observer T 21 (i) T 21 (j) Mesinger & Furlanetto 07 Peculiar velocities-III

Pair separation perpend. to line-of-sight r p (Mpc/h) Redshift-space Temperature-Temperature correlation function Pair separation along line-of-sight  (h -1 Mpc) Figures by Marco Pierleoni  s rprp No redshift distortions Model: Redshift: z=8  m =0.25,   =0.75 f(  m )= (  m ) 0.55 /b=0.5 b=2  100 km/s

Pair separation perpend. to line-of-sight r p (Mpc/h) Redshift-space Temperature-Temperature correlation function Pair separation along line-of-sight  (h -1 Mpc) Linear redshift distortions only. Flattening proportional to growth rate of density fluctuations.

Pair separation perpend. to line-of-sight r p (h -1 Mpc) Redshift-space Temperature-Temperature correlation function Pair separation along line-of-sight  (h -1 Mpc) Redshift distortions generating small-scale “spindle” due to nonlinear motions within virialized regions (100 km/s)

Pair separation perpend. to line-of-sight r p (h -1 Mpc) Redshift-space Temperature-Temperature correlation function Pair separation along line-of-sight  (h -1 Mpc) Geometry distortions (AP effect) from having assumed  m =1.00,   =0.00

Pair separation perpend. to line-of-sight r p (h -1 Mpc) Redshift-space Temperature-Temperature correlation function Pair separation along line-of-sight  (h -1 Mpc) All distortions included

MEASURING DENSITY FLUCTUATIONS Could be doable over a significant fraction of the cosmic time finding deviations from LCDM and measuring the dark energy at early stages (if any) Subarcminute resolution will be important (extended LOFAR)

- Measuring geometrical distortions in the iso-correlation contours of the 21 cm maps around the epoch of re-ionization allows to discriminate among competing dark energy models. -Measuring dynamical distortions in the iso-correlation contours of the 21 cm maps around the epoch of re-ionization allows to break the degeneracy between Dark Energy and Modified Gravity models and test the 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 map with deep galaxy redshift surveys. Results will depend on the relative bias of HI and galaxy which, however, can be determined self-consistently from the data

SKA and galaxies -I Blake, Abdalla, Bridle, Rawlings, 2004, aph Rawlings et al., 2004, aph Seo & Eisenstein 2003, ApJ, 598, 720 Abdalla & 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 (f sky /0.5) HI galaxies up to z=1.5 - probably the smallest masses probed will be 5x10 9 Msun - Shown is a model for which M bar ~ AM DM WMAPPLANCK 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, (f sky /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 Metcalf & White 2006 F sky= 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 effect Physics of inflation Adiabatic/isocurvature fluctuations Gaussianity Features 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.)