When the First Stars Formed How did we get from the “Big Bang” to a sky full of galaxies? Lincoln Greenhill Harvard-Smithsonian CfA Public lecture, U. Tas 05 Dec 8 NASA, ESA, S. Beckwith and the HUDF Team

Is this as far back in time as we can see ? What came before these galaxies?

Before the first galaxies Fireball of birth and a hot soup of radiation and matter

Temperature History Radiation Temperature z Matter Time 300,000 yr

Temperature History Radiation z Matter Time 300,000 yr 10 3 K Hydrogren Recombination Temperature

Temperature History Radiation z Matter Time 300,000 yr 10 3 K Last scattering of radiation by matter Matter and primeval radiation go separate ways Temperature

Structure at Recombination Background microwave emission remnant Very uniform!  T/T~10 -5 NASA/GSFC/WMAP Collab.

 T/T~10 -5 Structure at Recombination Background microwave emission remnant A far cry from stars and galaxies NASA/GSFC/WMAP Collab.

Temperature History Radiation z Matter Time 300,000 yr 10 3 K Temperature The Dark Ages (a sea of H) 0 yr

A Very Different Place when the First Stars… z 300,000 yr0 yr yr The Dark Ages First Luminous Objects Collapse of dark matter and cold Baryonic matter

Ecology at Recombination Matter = 13% normal + 87% “dark” on avg. Most matter in the universe appears to be DARK, apparently interacting only via gravity (Zwicky c.1933) Dark/normal matter are intermingled. Collapse of dark matter structures carries along normal matter. Baryogenesis

Collapse of Dark Matter during Reionization (Springel et al. 2005)

Time Collapse of baryonic matter into stars and galaxies z=20 Springel & Hernquist 2003

(Gnedin et al.)

Increasing transparency during reionization (Gnedin et al.)

How Can We Study the EOR? Radio imaging of the Hydrogen reservoir –The dominant component of the universe –Radiation not blocked by cosmic dust Hydrogen has rest frequency of 1420 MHz Mapping H in the nearby universe is routine. But at redshifts > 6 it appears at < 200 MHz –TV channels through 11 & FM radio –Trying to see stars from under a street lamp What comes next? –Find radio quiet locations –Build new observatories: the Epoch of Experimentation

Image courtesy of NRAO/AUI ; Yun, Ho, & Lo

MILEURA

A “traditional” radio observatory The Very Large Array New Mexico Operation 300 MHz- 50 GHz

Innovation for work below 200 MHz… The Mileura Wide-field Array / Low Frequency Demonstrator

“Mileura Wide-field Array Science and Technology Demonstrator,” a proposal to the NSF

Illustrated “Gulliver’s Travels” c When all is said and done, will we find the Epoch of Reionization? Yes or no, it will be one of the great challenges of astronomy and an adventure. Springel & Hernquist 2003