Cosmology Cosmic Structure content 1 st Asian Winter
- Slides: 58
Cosmology: Cosmic Structure & content 1 st Asian Winter School Pheonix Park, Korea (Jan 15, 2007) Tarun Souradeep I. U. C. A. A, Pune, India
India I. U. C. A. A. , Pune, India
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
The Realm of Cosmology Galaxy Clusters Size : Mega parsecs (Mpc. ) Mass : 100 – 1000 Galaxies (5% luminous, 15% hot gas, 80%dark matter !) Coma cluster
The Realm of Cosmology Super Clusters Size : 10 Mega parsecs Mass : few 1000 Galaxies Perseus super cluster
The Realm of Cosmology Distant galaxies beyond a cluster ….
The Realm of Cosmology …… most distant galaxies Hubble deep field
The Realm of Cosmology 100 million Light years
The Realm of Cosmology 100 million Light years
The Realm of Cosmology 500 million Light years
The Realm of Cosmology Few billion parsecs SLOAN DIGITAL SKY SURVEY (SDSS)
The Realm of Cosmology
How can we even hope to comprehend this immensely large & complex Universe !? ! Look for an appropriate simple model
The Isotropic Universe Distribution of galaxies on the sky is broadly isotropic Isotropy around every point implies Homogeneity Cosmological principle North Lick Observatory survey South
The Expanding Universe Einstein’s General relativity applied to an uniform distribution of matter on cosmic scales leads to a smooth expanding universe
The Expanding Universe Leads to the Hubble’s law Recession velocity is Proportional to the distance
Geometry of the Universe Spherical Universe Constant positive curvature Hyperbolic Universe Constant negative curvature Flat Universe
Geometry, Expansion & Matter
The Isotropic Universe Nobel prize 1978 Serendipitous discovery of the dominant Radiation content of the universe as an extremely isotropic, Black-body bath at temperature T 0=2. 725 (+/-0. 002)K. “Clinching support for Hot Big Bang model”
The dominant radiation component in the universe ~ 400 CMB photons per cubic cm. (D. Scott ’ 99)
The most perfect Black-Body spectrum in nature COBE –FIRAS The CMB temperature – A single number characterizes the radiation content of the universe!! COBE website
COBE-FIRAS results strongly constrain any Energy input into the CMB in the not-so-early universe (z<105) 60 Ghz 600 Ghz 10 GHz 30 GHz ARCADE 2004 10 Ghz 30 Ghz Next future: 3 -90 GHz (figs: Bond, 1996)
The Expanding Universe Expansion implies Hot early universe Smaller => hotter Wavelength of light is stretched by expansion Redshift, z=v/c Redshift is related to distance
Smaller Universe is Hotter ! MEASUREMENT of CMB temperature at higher-z 6. 0<T<14. 0 K at z=2. 33771 (Srianand, Petitjean, Ledoux in Nature 2000)
CMB isotropy strongly constrains Anisotropic Universe models (Fig: Amir Hajian)
Fingerprints of anisotropic cosmology (Fig: Amir Hajian, Ph. D thesis)
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)
Cosmic “Super–IMAX” theater 0. 5 Myr Here & Now (14 Gyr) 14 Transparent universe Opaque universe c P G
How much do we now know about this model Universe ? lots !!!
Matter budget of the Universe Ordinary (baryonic) matter Fig: NASA/WMAP science team
Ordinary matter is sprinkled on the Cold Dark matter distribution Galaxies light up at the densest points
Where is the Cold Dark matter ? Zwicky 1935 6 times more in dark matter than ‘baryonic’ matter
Rotation of Spiral Galaxies !!!
Dark matter in Galaxies ! R
Dark matter in our own backyard !? !
Dark matter in the Milky way
Dark matter in other galaxies too !!
Dark matter in clusters !? !
Speeding galaxies in a cluster Marbles in a glass bowl !!! Velocity dispersion of galaxies in a cluster Measures the depth of its gravitational potential
Hot gas in clusters Coma cluster
Hot gas in clusters Virgo cluster
Gravitational lensing Distant galaxies beyond a cluster are lensed….
Bullet cluster
Bullet cluster movie
Evidence for Dark Energy? Is it the Cosmological constant? The Cosmic repulsive force Einstein once proposed and later denounced as his ‘biggest blunder” ?
Geometry, Expansion & Matter Dark energy causes accelerated expansion
Correction to the Hubble’s Law Measure distances in the …. measures the acceleration independent of redshift v/c expansion of the universe till v/c=z~1
Measuring distance using standard candles 10 m Flux 4 Flux 5 m
Supernova in a galaxy: standard candle
Supernova can be seen in distant galaxies
Supernova in a very distant galaxy
• 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 Fig: NASA/WMAP science team • Starlight from Galaxies • Stuff we are made of!!
Total energy density Baryonic matter density Expansion rate of the universe Age of the universe Dark energy density Dark matter density Dawn of Precision cosmology !! NASA/WMAP science team
How do much we doknow we now so know much about now about this model Universe ?
Thank you !!! Music of the Cosmic Drum