Cosmology: Cosmic Structure

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Cosmology Cosmic Structure content
1st Asian Winter School Pheonix Park, Korea (Jan
15, 2007)
Tarun Souradeep
I.U.C.A.A, Pune, India
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India
I.U.C.A.A., Pune, India
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The Realm of Cosmology
Basic unit Galaxy
Size 10-100 kilo parsec (kpc.) Mass 100
billion Stars
Measure distances in light travel time 1 pc.
(parsec) 200,000 AU
3.26 light yr. Measure Mass in
Solar mass
Andromeda Galaxy
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The Realm of Cosmology
Galaxy Clusters
Size Mega parsecs (Mpc.) Mass 100 1000
Galaxies (5 luminous, 15 hot gas, 80dark
matter !)
Coma cluster
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The Realm of Cosmology
Super Clusters
Size 10 Mega parsecs Mass few 1000
Galaxies
Perseus super cluster
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The Realm of Cosmology
Distant galaxies beyond a cluster .
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The Realm of Cosmology
most distant galaxies
Hubble deep field
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The Realm of Cosmology
100 million Light years
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The Realm of Cosmology
100 million Light years
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The Realm of Cosmology
500 million Light years
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The Realm of Cosmology
Few billion parsecs
SLOAN DIGITAL SKY SURVEY (SDSS)
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The Realm of Cosmology
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How can we even hope to comprehend this immensely
large complex Universe !?!
Look for an appropriate simple model
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The Isotropic Universe
Distribution of galaxies on the sky is broadly
isotropic
Isotropy around every point implies Homogeneity
? Cosmological principle
South
North
Lick Observatory survey
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The Expanding Universe
Einsteins General relativity applied to an
uniform distribution of matter on cosmic scales
leads to a smooth expanding universe
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The Expanding Universe
Leads to the Hubbles law Recession velocity is
Proportional to the distance
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Geometry of the Universe
Spherical Universe Constant positive curvature
Hyperbolic Universe Constant negative curvature
Flat Universe
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Geometry, Expansion Matter
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The Isotropic Universe
Cosmic Microwave Background
Nobel prize 1978
Serendipitous discovery of the dominant
Radiation content of the universe as an
extremely isotropic, Black-body bath at
temperature T02.725 (/-0.002)K . Clinching
support for Hot Big Bang model
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Cosmic Microwave Background
The dominant radiation component in the universe
400 CMB photons per cubic cm.
(D. Scott 99)
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Cosmic Microwave Background
The most perfect Black-Body spectrum in nature
COBE FIRAS
The CMB temperature A single number characterize
s the radiation content of the universe!!
COBE website
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Cosmic Microwave Background
COBE-FIRAS results strongly constrain any Energy
input into the CMB in the not-so-early universe
(zlt105)
600 Ghz
(figs Bond, 1996)
ARCADE 2004
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The Expanding Universe
Expansion implies Hot early universe Smaller gt
hotter
Wavelength of light is stretched by expansion ?
Redshift, zv/c Redshift is related to distance
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Smaller Universe is Hotter !
MEASUREMENT of CMB temperature at
higher-z 6.0ltTlt14.0K at z2.33771
(Srianand, Petitjean, Ledoux in Nature 2000)
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Cosmic Microwave Background
CMB isotropy strongly constrains Anisotropic
Universe models
(Fig Amir Hajian)
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Fingerprints of anisotropic cosmology
(Fig Amir Hajian, PhD thesis)
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Cosmic Microwave Background
Pristine relic of a hot, dense smooth early
universe - Hot Big Bang model
Post-recombination Freely propagating through
(weakly perturbed) homogeneous isotropic
cosmos. Pre-recombination Tightly coupled to,
and in thermal equilibrium with, ionized matter.
(text background W. Hu)
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Cosmic SuperIMAX theater
0.5 Myr
14 GPc
Here Now (14 Gyr)
Transparent universe
Opaque universe
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How much do we now know about this model
Universe ?
lots !!!
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Matter budget of the Universe
Ordinary (baryonic) matter
FigNASA/WMAP science team
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Ordinary matter is sprinkled on the Cold Dark
matter distribution
Galaxies light up at the densest points
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Where is the Cold Dark matter ?
Zwicky 1935
6 times more in dark matter than baryonic
matter
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Rotation of Spiral Galaxies !!!
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Dark matter in Galaxies !
R
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Dark matter in our own backyard !?!
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Dark matter in the Milky way
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Dark matter in other galaxies too !!
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Dark matter in clusters !?!
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Speeding galaxies in a cluster
Marbles in a glass bowl !!! Velocity dispersion
of galaxies in a cluster Measures the depth of
its gravitational potential
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Hot gas in clusters
Coma cluster
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Hot gas in clusters
Virgo cluster
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Gravitational lensing
Distant galaxies beyond a cluster are
lensed.
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Bullet cluster
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Bullet cluster
movie
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Evidence for Dark Energy?
Is it the Cosmological constant? The Cosmic
repulsive force Einstein once proposed and later
denounced as his biggest blunder ?
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Geometry, Expansion Matter
Dark energy causes accelerated expansion
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Correction to the Hubbles Law
Measure distances independent of redshift
v/c till v/cz1
. measures the acceleration in the expansion
of the universe
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Measuring distance using standard candles
10 m
Flux
4 Flux
5 m
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Supernova in a galaxy standard candle
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Supernova can be seen in distant galaxies
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Supernova in a very distant galaxy
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• Accelerated expansion of the universe (High
  redshift SN)
• Structure formation scenario compatible with
  observations

Matter budget of the cosmos

• Rotation of galaxies
• Speeding galaxies in clusters
• Gravitational lensing
• Hot gas in clusters

• Light elements from early hot universe
• Low CMB temperature fluctuations

• Starlight from Galaxies
• Stuff we are made of!!

FigNASA/WMAP science team
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Total energy density
Baryonic matter density
Dark energy density
Expansion rate of the universe
Dawn of Precision cosmology !!
Dark matter density
Age of the universe
NASA/WMAP science team
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How much do we now know about this model
Universe ?
How do we know so much now about this model
Universe ?
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Thank you !!!
Music of the Cosmic Drum