From Avi Loeb

1. reionization From Avi Loeb

2. Quest to the Highest Redshift

3. Difficulties in finding high-z galaxies and quasars • Faint: m-M ~ 47, even the brightest galaxies need Keck/HST; only the brightest quasars can be detected with large surveys • Rare: e.g. z~6 quasar surface density is one per 500 sq. deg • Red: all spectral features shifted to the red part of the spectrum, Ly alpha at 1216x7 = 8500 A, where: • sky is very bright • CCD is very insensitive • Low surface brightness: SB ~ (1+z)-4 = 1/2400

4. High-redshift Galaxies/Quasars Searching Technique • Lyman break technique • Broad-band optical colors • Quasars – 80’s; galaxies – 90’s • Narrow-band imaging (Lyman alpha emitter) • Galaxies – 80’s • Slitless Spectroscopy • Wide-area spectroscopy • Looking for strong emission line • Quasars – 70’s; galaxies – now • Cross-identification with other wavelength • Radio: quasars – 60’s; galaxies – 60’s • X-ray: quasars – 80’s • Submillimeter: galaxies – 90’s • Serendipity (a.k.s. luck…) • If you are Hy Spinrad (Berkeley) or his student, then it will work…

5. So how far could each of these techniques go? • Lyman break: • Quasars: 6.4 • Galaxies: 6.6; maybe 10? • Narrow band imaging • Galaxies: 7.0 • Slitless spectroscopy • Quasars: 4.7 • Galaxies: 6.5 • Cross-identification • Quasars: 6.1 (radio) • Galaxies: 5.2 (radio) • Luck: • Quasars: 4.3 • Galaxies: 5.5

6. Lyman Break Galaxies I:Spectrum of high-z galaxies

7. Lyman break galaxies II:Colors of LBG Key: The presence of absorption at lambda < 1216A in the rest-frame UV of the galaxy produces a BREAK in the observed high-z galaxy spectrum: LYMAN BREAK by looking for “drop-out” objects in broad-band colors as a result of the Lyman break, we can find high-redshift galaxies!

8. Lyman break galaxies III:color selection

9. Narrow-band Imaging • Idea: • Young galaxies are dominated by young stars and star forming regions • With strong HII regions and strong Ly alpha emission lines • Looking for Lyman alpha line by looking for enhancement in the flux within narrow filters • High success rate, but still needs follow-up spectroscopy to eliminate contaminants: strong emission lines other than Ly-alpha

10. Matching towards high-z

11. The most distant galaxy known to date z=6.98

12. Even higher redshifts Z~10?

13. The new highest redshift record?

14. Lyman  Emitter at z~10? • Keck blind spectroscopic survey along critical lines of high-z clusters • Six promising Ly emitter candidates at z=8.7 - 10.2 • Limit of ground-based search; extremely difficult to confirm spectroscopically Stark, Ellis et al.

15. The history of star formation in the universe • Estimating star formation in a galaxy • Roughly proportional to the UV flux  UV flux comes from young, hot stars • Roughly proportional to the Lyman alpha flux  Lyman alpha emission comes from HII regions around young, hot stars • Madau plot: • Star formation volume density (including all galaxies) as a function of redshift • Rapid increase from z=0 to 1.5 • Slow decline at z>2

17. 46,420 Quasars from the SDSS Data Release Three 5 Ly forest 3 Ly 2 CIV redshift CIII MgII FeII 1 FeII OIII H 0 wavelength 4000 A 9000 A

18. 30 at z>6 60 at z>5.5 >100 at z>5

19. Strong density evolution Density declines by a factor of ~40 from between z~2.5 and z~6 Black hole mass measurements MBH~109-10 Msun Mhalo ~ 1012-13 Msun rare, 5-6 sigma peaks at z~6 (density of 1 per Gpc3) Quasars accreting at maximum rate Quasar luminosity consistent with Eddington limit Quasar Evolution at z~6 Fan et al. 2006, 2010

20. Quest to the Highest Redshift 090423 080913 050904 000131 GRBs 970228

21. z=8.2 GRB

22. A brief cosmic history • Big Bang: the universe filled with hot gas • Cosmic Dark Age: no light no star, no quasar • First light: the first galaxies and quasars in the universe • Cosmic Renaissance: universe lit up by young galaxies and quasars • “reionization” completed, the universe is transpartent and the dark ages ended  today

23. A brief cosmic history • Big Bang: the universe filled with hot gas • Cosmic Dark Age: no light no star, no quasar • First light: the first galaxies and quasars in the universe • Cosmic Renaissance: universe lit up by young galaxies and quasars • “reionization” completed, the universe is transpartent and the dark ages ended  today

24. When did 1-sigma peak collapse

25. Cooling Rate of Primordial Gas n=0.045 cm^-3 Atomic cooling H_2 cooling

26. Collapse Redshift of Halos Atomic cooling H_2 cooling 1-sigma 2-sigma 3-sigma 2-sigma

28. Binding Energy of Dark Matter Halos Supernova 3-sigma 1-sigma 2-sigma

29. Emergence of the First Star Clusters molecular hydrogen Yoshida et al. 2003

30. Z=30

31. First star simulation

32. Fate of first stars

34. Massive Accretion by Metal-Free Proto-Stars 0.5pc 25pc Bromm & Loeb

35. Simulation of a Hypernova Explosion Heavy elements 100 pc

36. The end of dark ages: Movie

37. Reionization • After recombination, the universe was neutral • At z~20 – 30, the first generation galaxies and mini quasars formed • At z~6 – 15, the UV radiation from the first generation objects ionized most of the HI in the universe • The neutral fraction of the universe changed from 1 to 10^-5 (phase transition in ionization state) • The temperature of the IGM electrons changed from CMB temperature to 10^4 (phase transition accompanied by temperature change) • IGM becomes transparent to UV radiation, the universe is like a giant HII region (temperature change accompanied by opacity change)

38. Neutral fraction Light background Gas density Gas temperature Gnedin 2000

39. Three stages Pre-overlap Overlap Post-overlap From Haiman & Loeb