Observational Cosmology

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Observational Cosmology

• Jonathan P. Gardner
• NASAs Goddard Space Flight Center

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Wilkinson Microwave Anisotropy Probe
Gary Hinshaw, WMAP Co-I
University of Edinburgh, September 3, 2004
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Hubble Space Telescope
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James Webb Space Telescope
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Astronomical Search For Origins
First Galaxies
Big Bang
Life
Galaxies Evolve
Planets
Stars
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Beginnings are Important (Origins)
David Jonathan Gardner, June 16, 2005
David Jonathan Gardner, June 16, 1998
... So Are Changes(Evolution)
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The First 13.7 Billion Years
Dark Matter/Dark Energy
Galaxies Evolve
Planets, Life Intelligence
First Galaxies
Atoms RadiationCMB
Particle Physics
Big Bang
Now
3 minutes
380,000 years
400 million years
1 billion years
7 billion years
13.7 billion years
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Edwin P. Hubble(the man, not the telescope)

1. Classification of Galaxies
2. The Spiral Nebulae are Island Universes
3. The Universe is Expanding

Edwin P. Hubble, 1889-1953
Which is further away?How can you tell?
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The Hubble Sequence

• Hubble classified nearby (present-day) galaxies
  into Spirals and Ellipticals.

• The Hubble Space Telescope extends this to the
  distant past.

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Measuring Distances
Cepheid Variable Stars known period-luminosity
relation.
Astronomers can measure distances if they know
the intrinsic luminosity.
Suitable for nearby galaxies
Supernovae known maximum luminosity. Suitable
for distant galaxies.
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Hubble Discovers the Universe
Cepheids in the Andromeda galaxy showed it is 8
times further than the most distant star in our
Galaxy. ? Island Universes!
Hubble at Mount Wilson telescope
Planetary Nebula are within our Galaxy.
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Doppler Shift
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Hubbles Law
Velocity in Kilometers per Second
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Looking Backwards in Time
Far, Far Away means Long, Long Ago

• Distance Light travel time Seeing the past.

1 Billion light years away 1 Billion years ago
Time
1 Million light years away, 1 Million years ago
Distance
Here Now
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The First Nano-Second
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How much of the Universe can we see?
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The Horizon Problem
Why is the cosmic microwave background
temperature so uniform on scales gt2?
T
T
O (10
)
-5


1
2
T
T
T
T
1
2
1
2
D gtgt c/H
o
q gtgt 2

MAP990008
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The Flatness Problem
Why is the universe anywhere close to W 1 now?

0
W 1 is an unstable stationary point.

0
Density 1ns after BB
447,225,917,218,507,401,284,015 gm/cc
Scale Factor a(t)
447,225,917,218,507,401,284,016 gm/cc
447,225,917,218,507,401,284,017 gm/cc
0
5
10
t Gyr
MAP990007
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Curved Space-Time
Flat, or Euclidean Space
Negative Hyperbolic Space
Positive Spherical Space
3D Figures by Stuart Levy of the University of
Illinois, Urbana-Champaign and by Tamara Munzer
of Stanford University for Scientific American.
2D Figures by Ned Wright, UCLA
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Inflation and a Flat Universe
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The Structure Problem
Clumpy distribution
of galaxies -
how did this happen?
Smooth 3K
Cosmic microwave
background radiation
MAP990012
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Inflation solves the problems
Later, the regions re-enter the horizon.Quantum
fluctuations become galaxies
Before Inflationcausally connected quantum
fluctuations.
After Inflation,previously connected regions are
outside the horizon.
Predictions Universe is flat. Fluctuations are
correlated on different scales.
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The First Three Minutes
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Synthesis of Light Elements

• Light elements, D, He, Li produced 3 minutes
  after Big Bang.
• One free parameter in predicted abundances
  baryon/photon ratio
• (note baryons atoms)
• Baryon/photon ratio now measured by CMB
  (discussed later).
• Predicted abundances may now be confronted with
  observed abundances (grey boxes). Some tensions.

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The First 380,000 Years
Wayne Hu and Martin White, Scientific American,
February 2004
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Why Bright Clumps?Remnants of Primordial
Oscillations
Gravity tries to make matter fall into potential
wells
Radiation pressure pushed back...
Oscillations results
Imprint of event imparted on photons...
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Sound Waves in the Plasma
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Baby Picture of the Universe
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WMAP shows the Universe is Flat
Dark Matter
Baryons
Flatness
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The First 400 Million Years
3s
2s
Cooling with atoms
1s
Cooling with H2
Barkana Loeb 2001, Physics Reports, 349, 125
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The First Galaxies

• What did the first galaxies to form look like?
• They are very distant, and very faint.

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Infrared Light

• Light from the first galaxies is redshifted from
  the visible into the infrared.

• Most of the Suns energy is visible light

• Infrared is heat radiation

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Deepest View(s) of the Universe

• 1995 Hubble Deep Field
• 10 days exposure, small area
• 1998 Hubble Deep Field South
• Repeat in another field
• 2003 Great Observatories Origins Deep Survey
• 30x area
• infrared with Spitzer, X-ray with Chandra
• 2004 Hubble Ultra-Deep Field
• 30 days exposure, more sensitive camera
• 1996-2006- Follow-up observations

Hubble Ultra Deep Field
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Hubble Ultra Deep Field
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Finding distant galaxies

• UV radiation shortward of Lyman limit at 912Å is
  absorbed by inter-galactic medium.
• This break is redshifted through successive
  filters

• Visible light technology (CCDs) ends at 1
  micron, so finding galaxies at zgt6 requires
  infrared.

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History of star-formation in the Universe
Star-formation density
Bouwens et al. 2005, astro-ph/0509641
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Prospects for future study at high-z

• Hubble (2.4m diameter warm telescope)
• Reaches to z6, with claims to 7 or 8.
• New camera to be installed in next servicing
  mission may reach to magnitudes of 28.5 (15 nJy)
  in the NIR.
• No longer has sensitive spectroscopic capability
  in opt-NIR.
• Spitzer (0.85m diameter cold telescope)
• Reaches to z6 (same galaxies as HST).
• Reaches magnitudes of 26.6 in near- to mid-IR.
• Ground-based observations (10m warm)
• Limited by atmosphere

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How to win at Astronomy
1010
Photographic electronic detection
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Telescopes alone
HST
CCDs
Big Telescopes with Sensitive Detectors in Space
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Sensitivity Improvement over the Eye
Photography
1796
1926
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1665
102
1610
Rosses 72
Mount Wilson 100
Mount Palomar 200
Soviet 6-m
Shorts 21.5
Herschells 48
Slow f ratios
Huygens eyepiece
Galileo
1600
1700
1800
1900
2000
Adapted from Cosmic Discovery, M. Harwit
Year of observations
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HST vs. JWST - temperature
-225 Celsius,-370 Fahrenheit
Room Temperature
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HST vs. JWST - orbit
How will JWST get there?
375 miles up
Second Lagrange Point,1,000,000 miles away
Ariane 5
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HST vs. JWST - size
How do you put a 6.5 meter mirror in a 5 meter
rocket?
2.4 meter diameter
6.5 meter diameter
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The First 1 Billion Years
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When was re-ionization?
Fan et al. 2001, AJ, 122, 2833
Fan et al. 2001, AJ, 122, 2833
Kogut et al. 2003, ApJS, 148, 161
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The First 7 Billion Years
M81 by Spitzer
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Distant Galaxies are Train Wrecks

• Trace construction of Hubble sequence

• How do train wrecks become spirals and
  ellipticals?

By Merging!
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Galaxy Mergers
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The Last 7 Billion Years
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The Next 20 Years

• What is the cause of inflation?
• What is the dark energy?

In other words

• How did the Universe begin?
• How will it end?

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Can We Prove Inflation?

• Gravity waves propagating during inflation leave
  a mark on the polarization of the CMB.
• CMB Polarization mission
• Currently being studied.

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What is the Dark Energy?

• Hypothesized by Einstein, discovered in 1998,
  confirmed in 2003.
• 3 potential Nobel Prizes
• Cosmological Constant breaks standard model of
  particle physics
• Quintessence means new physics
• Modification of General Relativity
• NASA-DOE Joint Dark Energy Mission
• Currently being studied.

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Observational Cosmology

• Jonathan P. Gardner
• NASAs Goddard Space Flight Center