Reionization of the Universe MinGyu Kim

Reionization of the Universe Contents Cosmology 0. Frontier of small scale structures 1-1. Formation and evolution of CDM Halos 1-2. Formation of the First objects 2-1. Observational probes of the reionization era and further deep universe (dark ages) 2-2. Challenges for the future & Summary

Reionization of the Universe Introduction Cosmology

Reionization of the Universe Contents Cosmology 0. Frontier of small scale structures 1-1. Formation and evolution of CDM Halos 1-2. Formation of the First objects 2-1. Observational probes of the reionization era and further deep universe (dark ages) 2-2. Challenges for the future & Summary

Reionization of the Universe From simplicity to complexity Cosmology CMB shows large homogeneous and isotropic with small fluctuations. Present LSS are originated from small- amplitude density fluctuations. In the so called bottom-up hierarchy, galaxies were assembled out of building blocks of smaller mass.

Reionization of the Universe Contents Cosmology 0. Frontier of small scale structures 1-1. Formation and evolution of CDM Halos 1-2. Formation of the First objects 2-1. Observational probes of the reionization era and further deep universe (dark ages) 2-2. Challenges for the future & Summary

Reionization of the Universe Linear Gravitational Growth Cosmology In a homogeneous universe, (we impose small perturbations) Then the fluid is described by, (continuity and euler equation) where, For small perturbations δ ≪ 1, (fluid equation is linearized by) The spatial fluctuation is described by, and governs,

Reionization of the Universe Formation of nonlinear objects Cosmology Perturbation δ ~ 1, (full non-linear gravitational problem must be considered) Collapse of a spherical top-hat is described by Newtonian equation, (with a correction for the cosmological constant) Density profiles for the result halos are described by, where,

Reionization of the Universe Abundance of DMH Cosmology

Reionization of the Universe Gas infall and cooling in DMH Cosmology Minimum halo mass of baryonic object is described by,

Reionization of the Universe How about chemistry Cosmology First objects were formed only through cooling by H 2 However, H 2 is fragile and can easily be photo-dissociated by photons (with energies of ~ 13.6eV) Soon after trace amounts of stars form, the formation of additional stars due to H 2 cooling is suppressed.

Reionization of the Universe How about chemistry Cosmology Further fragmentation is possible only through atomic line cooling.

Reionization of the Universe Contents Cosmology 0. Frontier of small scale structures 1-1. Formation and evolution of CDM Halos 1-2. Formation of the First objects 2-1. Observational probes of the reionization era and further deep universe (dark ages) 2-2. Challenges for the future & Summary

Reionization of the Universe The birth and death of the first stars Cosmology

Reionization of the Universe The birth and death of the first stars Cosmology

Reionization of the Universe Pop Ⅰ vs. Pop Ⅲ Cosmology Richard B. Larson et al., 2004

Reionization of the Universe Gas property simulation Cosmology Z ~ 31.2

Reionization of the Universe Gas and clump morphology Cosmology Z ~ 28.9

Reionization of the Universe Metal free or Metal poor Cosmology Fernandez et al., 2006

Reionization of the Universe Radiative feedback from the first sources of light Cosmology 1) Escape of ionizing radiation from Galaxies. 2) Reionization of the IGM. 3) Suppression of the formation of low mass galaxies. 4) Propagation of supernova outflows in the IGM and its effects.*

Reionization of the Universe Radiative feedback from the first sources of light Cosmology 1) Escape of ionizing radiation from Galaxies. Reionization is determined by the amount of ionizing radiation escaping from the host galaxies of stars and quasars. Gas within halos is far denser than the typical density of the IGM. We can expect that the escape fraction of high redshift is much lower than that of present day because of high densities. Numerical simulations of reionization are limited in their resolution of the densest regions and in the accuracy of their treatment of radiative transfer. Also, we don’t know the clumpiness and hydrodynamic feedback which is expelled from the disk by stellar winds and supernovae.

Reionization of the Universe Radiative feedback from the first sources of light Cosmology 2) Reionization of the IGM.

Reionization of the Universe Radiative feedback from the first sources of light Cosmology 2) Reionization of the IGM. z=7.7 z=6.7

Reionization of the Universe Radiative feedback from the first sources of light Cosmology 3) Suppression of the formation of low mass galaxies. Before reionization, the IGM is cold and neutral ->cooling is dominant. ->High star formation rate After reionization, heating the IGM -> Jeans mass is increased. -> suppress the star formation rate

Reionization of the Universe Feedback from galactic outflows Cosmology 4) Propagation of supernova outflows in the IGM and its effects.* Massive stars are resulted in supernova explosion. Outflow enrich the metal abundance in the IGM. Outflows may have had a great impact on the earliest generations of galaxies M > 8M solar star ejects mass of ~3M solar -> explodes for 126M solar of star formation

Reionization of the Universe What kinds of sources are there ? Cosmology 1)Galaxies 2)Quasars 3)Supernova 4)Gamma ray burst

Reionization of the Universe 1) Galaxies Cosmology

Reionization of the Universe 2) Quasars Cosmology

Reionization of the Universe 3) Supernova Cosmology

Reionization of the Universe 4) Gamma Ray Burst Cosmology

Reionization of the Universe Where are we now ? Cosmology We know very early universe (z~1100) and the universe z < 8. We have a lot of theories between them. We need more observational result to prove one of those theories or some other new theories should be found.

Reionization of the Universe Contents Cosmology 0. Frontier of small scale structures 1-1. Formation and evolution of CDM Halos 1-2. Formation of the First objects 2-1. Observational probes of the reionization era and further deep universe (dark ages) 2-2. Challenges for the future & Summary

Reionization of the Universe Various kinds of methods Cosmology Search high-z objects Cosmology with Lyα photons From CMB anisotropies 21cm Tomography Lower bound : Upper bound :

Reionization of the Universe Various kinds of methods Cosmology Search high-z objects Cosmology with Lyα photons From CMB anisotropies 21cm Tomography Lower bound : Upper bound :

Nearby vs. Distant Reionization of the Universe Cosmology z=0.158 z=3.62 Gunn & Peterson trough

Reionization of the Universe The most distant galaxy so far Cosmology

Reionization of the Universe Cosmology with Lyα photons Cosmology Lyα ~ 121.5nm Peak is around 1400nm which corresponds to the z ~ 10 Stellar emission H1 absorption

Reionization of the Universe Various kinds of methods Cosmology Search high-z objects Cosmology with Lyα photons From CMB anisotropies 21cm Tomography Lower bound : Upper bound :

Reionization of the Universe From CMB anisotropies Cosmology All baryonic matter was ionised until 3x10^5 yrs old (τ→∞ ). At z~1100, the electrons and ions combined to form atoms (τ ≪ 1) WMAP measured τ~0.17±0.04

Reionization of the Universe 21cm Tomography Cosmology The energy sources of reionization and the structure formation during reionization. The 21cm line in hydrogen is potentially a means of studying this period, so called the "dark ages" that preceded reionization. By studying 21-cm line emission, we can do that.

The evolution of the IGM z dec ~150: compton heating. T k = T cmb before z dec ; T k ~(1+z) 2 after. z 1 : T s = T k (collisional coupling)before z 1 ; T s  T cmb (radiative coupling)after. z h : IGM T k > T cmb. (X-ray heating by galaxies) z c : Wouthuysen-Field Effect couples T s = T k again(Lya). z r : reionization ended. z dec ~150: compton heating. T k = T cmb before z dec ; T k ~(1+z) 2 after. z 1 : T s = T k (collisional coupling)before z 1 ; T s  T cmb (radiative coupling)after. z h : IGM T k > T cmb. (X-ray heating by galaxies) z c : Wouthuysen-Field Effect couples T s = T k again(Lya). z r : reionization ended.

Reionization of the Universe 21cm brightness Temperature Cosmology Stevan R. Furlanetto et al., 2006

Reionization of the Universe Contents Cosmology 0. Frontier of small scale structures 1-1. Formation and evolution of CDM Halos 1-2. Formation of the First objects 2-1. Observational probes of the reionization era and further deep universe (dark ages) 2-2. Challenges for the future & Summary

Reionization of the Universe Direct measurement ? Cosmology CMB anisotropies from Planck mission will soon be coming out. DARE & SKA are about to start observations of 21cm from Dark ages. JWST & SPICA will be launched within a decade.

Reionization of the Universe Summary Cosmology We know big picture but not in details yet. WMAP makes us having convincing that we are doing in right way. Improvement speed of instrumental science is exponentially increases. Details of reionization era will prove the structure formation and evolution of the first object.