From Avi Loeb reionization

Quest to the Highest Redshift

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

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…

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

Lyman Break Galaxies I: Spectrum of high-z galaxies

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!

Lyman break galaxies III: color selection

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

Matching towards high-z

The most distant galaxy known to date z=6.98

Even higher redshifts Z~10?

The new highest redshift record?

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

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

46,420 Quasars from the SDSS Data Release Three wavelength 4000 A9000 A redshift Ly  CIV CIII MgII HH OIII FeII Ly  forest

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

Quasar Evolution at z~6 Strong density evolution –Density declines by a factor of ~40 from between z~2.5 and z~6 Black hole mass measurements –M BH ~ M sun –M halo ~ M sun –rare, 5-6 sigma peaks at z~6 (density of 1 per Gpc 3) Quasars accreting at maximum rate –Quasar luminosity consistent with Eddington limit Fan et al. 2006, 2010

Quest to the Highest Redshift GRBs

z=8.2 GRB

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

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

When did 1-sigma peak collapse

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

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

Binding Energy of Dark Matter Halos 1-sigma2-sigma 3-sigma Supernova

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

Z=30

First star simulation

Fate of first stars

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

Simulation of a Hypernova Explosion 100 pc Heavy elements

The end of dark ages: Movie

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)

Gnedin 2000 Neutral fraction Light background Gas densityGas temperature

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