# Presentation: 468691

## Andrea Ferrara 

*Andrea Ferrara *
*SISSA/International School for Advanced Studies*

- Reionization Signatures of First Stars

## The Dark Ages

-  The gas cools and becomes neutral: recombination

-   The first structures begin to form:
-       reionization starts

-  Reionization is complete

-  Today’s structures

- UV/Optical/IR

- FIR/Radio?

- THE MOST DISTANT OBJECTS

- LYMAN ALPHA EMITTERS

*Iye+ 2006, Kashikawa+ 2006, Nagao+ 2007*

## The Dark Ages

-  The gas cools and becomes neutral: recombination

-   The first structures begin to form:
-       reionization starts

-  Reionization is complete

-  Today’s structures

- Years since
- the Big Bang
- ~350000
- (z~1000)
- ~100 million
- (z~20-30)
- ~1 billion
- (z~6)
- ~13 billion
- (z=0)

- UV/Optical/IR

- FIR/Radio?

- LENSED DROPOUT AT z=6.56

- THE MOST DISTANT OBJECTS

*Hu+ 2002, Santos+ 2006, Bouwens+ 2006, Pello+ 2006*

## Lyman Alpha Equivalent Width of Pop III Stars

- LYMAN ALPHA EMITTERS

- DIAGNOSTICS

- Salpeter 1-500 M

- IMF

*Scannapieco+ 2002*

- Salpeter 50-500 M

## The Dark Ages

-   The first structures begin to form:
-       reionization starts

-  Reionization is complete

-  Today’s structures

- UV/Optical/IR

- FIR/Radio?

- COSMIC STAR FORMATION

- THE MOST DISTANT OBJECTS

*Hopkins 2006*

## Lots of hidden/missing high-z star formation

-       reionization starts

-  Reionization is complete

-  Today’s structures

- The Dark Ages

- UV/Optical/IR

- FIR/Radio?

- HIGH-z star formation

- THE MOST DISTANT OBJECTS

*Stark+ 2006*

- Observed

- Integrated
- to L=0.1 L*

- Integrated
- to L=0

- Lots of hidden/missing high-*z* star formation

## Total Metallicity

- CHEMICAL FEEDBACK

-  COSMIC POPIII/POP II TRANSITION

*Tornatore, AF & Schneider 2007*

- Fraction of PopIII forming sites

*z=5*

*z=3*

*z=3*

*z=5*

- PopIII wave

*Pop III*

*Pop II*

## PopII

- CHEMICAL FEEDBACK

-  STAR FORMATION RATES

*Tornatore, AF & Schneider 2007*

- PopIII

*******Z*******M

## Spitzer/IRAC data

-  FLUCTUATIONS

- POPII

- POPIII

*Salvaterra**+ **200**6, Thompson+ 2007a,b*

*Kashlinsky+ 2005, 2007*

- NEAR INFRARED BACKGROUND

## 5  z  9 galaxies

- NEAR INFRARED BACKGROUND

-  INTENSITY

*Salvaterra**+ 2006, Fernandez & Komatsu 2006*

*5 **** z **** 9 galaxies*

## Scannapieco+ 2006

- FIRST STARS IN THE MILKY WAY

*Scannapieco+ 2006*

**Notes:**
Fixed physical size of 250 proper kpc^3

## FIRST STARS IN THE MILKY WAY

## FIRST STARS IN THE MILKY WAY

## FIRST STARS IN THE MILKY WAY

## FIRST STARS IN THE MILKY WAY

## Galactic Archaeology:

- FIRST STARS in the milky way

- HALO METAL-POOR STARS

*Salva**dori+ 2007*

- The Metallicity Distribution Function

**See poster by Stefania Salvadori**

## Reionization History

## REIONIZATION TESTS

## Lyα optical depth

- REIONIZATION TESTS

-  GUNN-PETERSON EFFECT

- Lyα optical depth

- TRASMISSION

- ABSORPTION

***(1+z)**4.3*

***(1+z)**>10*

*Fan 2006*

## τe = 0.09 ± 0.03

*τ**e** = 0.**09 **± 0.0**3*

- Polarization Maps
- Q Stokes Parameter

- REIONIZATION TESTS

- WMAP3 RESULTS

##  Choudhury & AF 2005, 2006

* **Choudhury & AF **2005, **200**6*

-    Self-consistent treatment of the evolution of ionized regions and thermal history

-    Follow evolution of neutral, HII and HeIII regions

-    Three sources of ionizing radiation:
- 	  PopIII stars: early redshifts, *Salpeter IMF*, zero metallicity
- 	  PopII  stars: Salpeter IMF, PopIII-PopII transition included
- 	  Quasars: significant @ z < 6, using -MBH relation

-    Radiative feedback suppressing SF in low-mass halos, set by:
- 	  Molecular cooling in neutral regions
- 	  Photoionization temperature in ionized regions

- GLOBAL REIONIZATION MODELS

##  Choudhury & AF 2005, 2006

- GLOBAL REIONIZATION MODELs

- GRB

- LAEs

- G-P

## Halo Mass [M]

- NATURE OF REIONIZATION sources

- Halo Mass [M]

- IONIZING PHOTON BUDGET

***z = 7***

*f**** *> 80% of the ionizing power
-    from *M* < 109 *M* halos

## Current candidate high-z galaxies:  2%  of ionizing budget!

- NATURE OF REIONIZATION sources

- OBSERVING THE SOURCES

- AB mag

- HUBBLE UDF

- Halo mass

- Counts

- Current candidate high-z galaxies:  2%  of ionizing budget!

## Neutral Hydrogen Fraction

- tQ = 2 × 107  yr,  Nγ  =5.2 × 1056 s-1, *z*=6.3,* * xHI > = 0.1

* **Maselli, Gallerani & AF 2007*

- QSO HII REGIONS

- NEW REIONIZATION TESTS

-  142 h-1 Mpc

## ‹ xHI›=1

- ‹ xHI›=1

- ‹ xHI›=0.1

- ‹ xHI›= 2.3 × 10-4

- QSO HII REGIONS

- Additional REIONIZATION TESTS

## xHI<0.06 @ z=6.13

- Rd

- NEW REIONIZATION TESTS

- QSO HII REGIONS

*Maselli, Gallerani & AF 2006*

***x******HI******<******0.06****** @ z=******6.13***

- based on the analysis of Fan (2006) QSO sample

## SIMULATED SPECTRA

***SIMULATED SPECTRA***

- NEW REIONIZATION TESTS

- GAP STATISTICS

*Gallerani+ 2006, 2007*

- Early Reionization Model

- Late Reionization Model

## xHI<0.36 @ z=6.3

- New REIONIZATION TESTS

- GAP STATISTICS

*Gallerani, AF, Fan & Choudhury 2007*

- Early

- Early

- Late

- Late

***x******HI******<******0.36****** @ z=******6.3***

##  Growing evidences of early (PopIII ?) SF: stellar mass, NIRB, reionization, EMPS

-  Growing evidences of early (PopIII ?) SF: stellar mass, NIRB, reionization, EMPS
-  Transition to normal stars occurs when *Z  **>**  Z**crit **~  10**-5**±**1** Z*; strongly governed by dust
*  *Pop III SF continues to *z **~** 3** *at periphery of collapsing structures. Observable in LAEs ?* *
-  Reionization started by metal-free stars @ *z*=20; 90%  complete @ *z*=8
-  Early Reionization  (*z* > 7) not in contrast  with any QSOAL test  (GP, Gaps, HII regions)
* **f**** *> 80% of the ionizing power at *z*  7 from halos of *M* < 109 *M*
-  Bulk of reionization sources not observed yet. Need JWST ?

- SELECTED SUMMARY