End of the Cosmic Dark Ages -- the First Galaxies and the Cosmic Renaissance

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End of the Cosmic Dark Ages-- the First
Galaxiesand the Cosmic Renaissance

• Xiaohui Fan
• Steward Observatory
• The University of Arizona

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Prelude an offer fromVera Rubin
During the conference After the Dark Ages when
Galaxies were young In Oct 1998, near Washington
DC.
Martian meteorite Will be awarded the discoverer
of the first redshift higher than seven object
still unclaimed
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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
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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
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The end of dark ages Movie
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Cold gas
Light background
Gnedin 2000
Gas density
Gas temperature
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Cold gas
Light background
Gas density
Gas temperature
Gnedin 2000
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Life as a Hydrogen atom at the end of cosmic dark
ages
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To Study the End of Cosmic Dark Ages is to

• Search for the first light ? the earliest and
  most distant galaxies and quasars in the universe
• Map the history of the cosmic enlightenment ? how
  the light from the first galaxies and quasars
  transformed the universe from opaque to
  transparent, reionize the universe and ended
  the cosmic dark ages
• ? The cosmic history in the first billion
  years after the Big Bang

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A tale of Two Maps

• Sloan Digital Sky Survey mapping the optical
  sky
• Finding the first quasars
• Discovery of Gunn-Peterson effect shadow of the
  cosmic dark ages
• Wilkinson Microwave Anisotropy Probe mapping
  the microwave sky
• Polarization of the cosmic microwave background
  looking through the cosmic dawn

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Redshift measuring distance in cosmology

• Redshift measures of how fast an object is moving
  away from us ? they are redder, or their
  spectral lines are at longer (redder) wavelength
• http//skyserver.sdss.org/en/proj/advanced/hubble/
  doppler.swf
• Expansion of the universe ? more distant objects
  move faster away from us, or at higher redshift
• Light from the most distant objects took the
  longest time to reach us ? highest redshift
  objects are the youngest, or earliest objects
  in the universe
• Searching for the first objects in the universe ?
  searching for the most distant, highest-redshift
  galaxies and quasars
• z7
• 13 billion light years away
• the universe was about 700 million years old 5
  of its current age.

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Quest to the Most distant Quasars and Galaxies
Z7 Dr. Rubins Meteorite??
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What is a Quasar?

• Quasar Quasi-Stellar Object (QSO)
• Very luminous (100 1000 brighter than Milky
  Way)
• Active nucleus at the center of galaxy
• Powered by supermassive black holes (millions
  solar masses)
• Radiation from hot gas falling into BH
• Among the most distant objects in the universe

Ground-based Image stellar
Gas and dust surrounding The central BH
At the center of galaxy
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Quasar Spectra at Different Redshifts
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SDSS Technical Goals
MAKE A DIGITAL 3-D MAP OF THE UNIVERSE IN 5
YEARAS

• Main Imaging Survey
• 10,000 square degrees
• ¼ of the whole sky
• 100 million 5-band images

• Spectroscopic Survey
• brightest 1 million galaxies
• brightest 100,000 quasars

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Where is the SDSS?
The SDSS telescopes are located at Apache Point
Observatory (APO) in the Sacramento Mountains of
south-central New Mexico.
Just down the road is the National Solar
Observatory in Sunspot, New Mexico. Both
Observatories and a nearby Visitors Center are
open to the public.
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SDSS Technological Inovations

• 2.5m Dedicated Telescope
• with wide 3o field-of-view
• Largest CCD Imaging Camera
• 54 large CCD devices, 150 Mega pixels
• Filters ugriz (3000-11000 A) for
  star/galaxy/QSO selection
• Data rate 15 deg/hr 5MB/s 170 GB/night 12
  TB total
• Multiobject Fiber Spectrographs
• 640 different objects observed at the same
  time.
• Large Volume Data processing
• Many terabytes of raw data, processed at
  Fermilab

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Apache Point Observatory
ARC 3.5m Telescope
SDSS 0.5m Telescope
SDSS 2.5m Telescope
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SDSS 2.5m Telescope
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SDSS Imaging Camera Top to bottom g z
u i r
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What does the data actually look like?
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Plugging Spectroscopic Plates
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Survey Participants
Participating Institutions 100 Scientists
Princeton University University of
Chicago Fermilab Institute for Advanced
Study Johns Hopkins University University of
Washington U.S. Naval Observatory Japanese
Participation Group New Mexico State
University Max-Planck A and IA
Funding 100 Million
Alfred P. Sloan Foundation Member
Institutions National Science Foundation
(NSF) National Aeronautics and Space
Administration (NASA) United States Department of
Energy (DOE) Japanese Monbukagakusho The Max
Planck Society
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The SDSS Collaboration
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How to find the most distant quasars?

• The highest redshift, most distant quasars are
  very red ? looking for the reddest objects on the
  sky
• The highest redshift, most distant quasars are
  extremely rare ? one out of many million objects,
  and could be confused with many kinds of
  contaminants brown dwarfs, cosmic ray hits
  etc. ? needles in a haystack ? complicated,
  multi-step searching technique that involves a
  number of follow-up observation using
  telescopes in addition to the SDSS facilities.

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Find the most distant quasarsneedles in a
haystack
Hobby-Eberly (Texas) 9.2m
APO 3.5m
Keck (Hawaii) 10m
Calar Alto (Spain) 3.5m

• SDSS database
• 40 million objects

4. Detailed spectra (8 new quasars at z6
2..Photometric pre-selection 200 objects
3. Photometric and spectroscopic Identification
(20 objects)
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Search for the First Quasars Results

• 3000 square degrees of the sky searched
• 6 telescopes, 10 different instruments used
• Spent 3 years, 50 nights of observing time
• 8 most distant quasars discovered
• z5.74, 5.82, 5.85, 5.99
• 6.05, 6.23, 6.28, 6.37

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Z6 quasars from the SDSS
Z5.80
Z5.82
Z5.99
Z6.28
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New z6 Quasars from the SDSS
z6.1
z6.2
z6.4
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The most distant quasar probing the state of
universe at the end of the dark ages, by
looking at the absorption from cold gas in the
quasar spectrum from before the end of the dark
ages.
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Neutral fraction
Light background
Gas density
Gas temperature
Gnedin 2000
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Gunn-Peterson Effect Shadow of the Dark Ages

• Gunn-Peterson (1965) effect
• During the dark ages, the universe is opaque to
  the ultraviolet light due to the cold, neutral
  hydrogen
• Create a absorption TROUGH in the quasar spectrum
• Detection of Gunn-Peterson trough signals that we
  have reached the cosmic dark-age and the epoch
  of the first generation galaxy and quasar
  formation
• One of the longest-sought predictions of
  cosmology, but never detected until

Lya
No G-P trough (still flux detected)
G-P trough
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VLT/FOS2
Detection of A Complete Gunn-Peterson Trough
We have reached The end of the Cosmic dark ages
T-0.0010.003
Pentericci et al.

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Detection of Gunn-Peterson Trough Tells us

• At z6 (800 million years after the big bang)
• The universe is going through a rapid transition
• Cold ? hot
• Neutral ? ionized
• Opaque ? transparent
• First generation galaxies and quasars have formed
• Cosmic Dawn has arrived!
• the End of the Cosmic Dark Ages
• Question
• when did this transformation started?
• when was the very first star form?
• How long did the cosmic renaissance last?

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WMAP Wilkinson Microwave Anisotropy Probe
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First detailed full sky CMB map afterglow of the
big bang
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Fluctuation on the cosmic micronwave background
finger print of the cosmos
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CMB polarization looking through the cosmic dawn

• CMB fluctuation seeds of todays galaxies and
  quasars
• First galaxies and quasars heated and ionized
  the universe at the end of the dark ages ? cosmic
  dawn
• Ionized plasma in cosmic dawn polarizing the
  microwave background
• Amount of polarization ? determining the exact
  onset of the cosmic dawn

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Polarization how it works
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Polarization how do we see it
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WMAP detecting polarization
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WMAP Polarization Results

• CMB is strongly polarized
• A lot of hot plasma from the first galaxies and
  quasars
• The first star were formed at about 300 million
  years after the big bang, starting the cosmic
  dawn
• The cosmic renaissance the reionization epoch
  -- lasted for half billion years ? the cosmic
  dark ages didnt end in one night!
• However
• CMB result is still an indirect result
• The very first light has not been detected
• The detailed history of cosmic renaissance yet to
  be mapped out

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The Decade of Galaxy Formation

• In the next 10 15 years, a number of large
  ground-based and space telescope will be built
• One of the central goal of these telescopes
  detecting the first light, probing deep into the
  cosmic dark age, and mapping of the history of
  cosmic reionization and formation of first
  galaxies and quasars

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The James-Webb Space Telescopethe first light
machine
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Atacama Large Millimeter Arraystar formation in
the early universe
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Square Kilometer ArrayDetecting Hydrogen in the
Dark Ages
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PlanckMapping the reionization history
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20-30 meter ground-based telescopes probing the
high-redshift universe
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Summary

• As of 2003, people have discovered galaxies and
  quasars up to redshift of 6.5, or 13 billion
  light years away, coming from a time when the
  universe was only 5 - 6 its current age
• We believe we have detected the epoch of the end
  of cosmic dark ages, when the first galaxies and
  quasars in the universe were forming, and lit up
  the whole universe
• In the next two decades, new telescopes, from the
  ground and in space, will systematically explore
  the high-redshift universe, likely discovered the
  first light in the universe and map out the
  history of the cosmic dark ages.