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Observational Cosmology Jonathan P. Gardner NASA’s Goddard Space Flight Center
Wilkinson Microwave Anisotropy Probe Gary Hinshaw, WMAP Co-I University of Edinburgh, September 3, 2004
Astronomical Search For Origins First Galaxies Big Bang Life Galaxies Evolve Planets Stars
Beginnings are Important …(Origins) David Jonathan Gardner, June 16, 2005 David Jonathan Gardner, June 16, 1998 ... So Are Changes(Evolution)
The First 13.7 Billion Years Dark Matter/Dark Energy Galaxies Evolve Planets, Life & Intelligence First Galaxies Atoms & Radiation:CMB Particle Physics Big Bang Now 3 minutes 380,000 years 400 million years 1 billion years 7 billion years 13.7 billion years
Edwin P. Hubble(the man, not the telescope) • Classification of Galaxies • The “Spiral Nebulae” are “Island Universes” • The Universe is Expanding Edwin P. Hubble, 1889-1953 Which is further away?How can you tell?
The Hubble Sequence • Hubble classified nearby (present-day) galaxies into Spirals and Ellipticals. • The Hubble Space Telescope extends this to the distant past.
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.
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.
Hubble’s Law Velocity in Kilometers per Second
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 Here & Now Distance
The Horizon Problem Why is the cosmic microwave background temperature so uniform on scales >2°? T = T + O (10 ) -5 1 2 T T T T 1 2 1 2 D >> c/H o q >> 2 ° MAP990008
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
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
The Structure Problem Clumpy distribution of galaxies - how did this happen? Smooth 3K Cosmic microwave background radiation MAP990012
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.
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.
The First 380,000 Years Wayne Hu and Martin White, Scientific American, February 2004
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...
WMAP shows the Universe is Flat Dark Matter Baryons Flatness
The First 400 Million Years 3σ 2σ Cooling with atoms 1σ Cooling with H2 Barkana & Loeb 2001, Physics Reports, 349, 125
The First Galaxies • What did the first galaxies to form look like? • They are very distant, and very faint.
Infrared Light • Most of the Sun’s energy is visible light • Light from the first galaxies is redshifted from the visible into the infrared. • Infrared is heat radiation
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
Infrared 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 z>6 requires infrared.
History of star-formation in the Universe Star-formation density Bouwens et al. 2005, astro-ph/0509641
Prospects for future study at high-z • Hubble (2.4m diameter warm telescope): • Reaches to z~6, 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 z~6 (same galaxies as HST). • Reaches magnitudes of 26.6 in near- to mid-IR. • Ground-based observations (10m warm) • Limited by atmosphere
JWST How to win at Astronomy 1010 Photographic & electronic detection 108 Telescopes alone HST CCDs Big Telescopes with Sensitive Detectors in Space 106 Sensitivity Improvement over the Eye Photography 1796 1926 104 1665 102 1610 Rosse’s 72” Mount Wilson 100” Mount Palomar 200” Soviet 6-m Short’s 21.5” Herschell’s 48” Slow f ratios Huygens eyepiece Galileo 1600 1700 1800 1900 2000 Adapted from Cosmic Discovery, M. Harwit Year of observations
HST vs. JWST - temperature -225° Celsius,-370° Fahrenheit Room Temperature
HST vs. JWST - orbit How will JWST get there? 375 miles up Second Lagrange Point,1,000,000 miles away Ariane 5
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
Redshift Neutral IGM z~zi z>zi . z<zi Wavelength Wavelength Wavelength Lyman Forest Absorption Patchy Absorption Black Gunn-Peterson trough 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
The First 7 Billion Years M81 by Spitzer
Distant Galaxies are “Train Wrecks” • Trace construction of Hubble sequence: • How do “train wrecks” become spirals and ellipticals? By Merging!
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?
Can We Prove Inflation? • Gravity waves propagating during inflation leave a mark on the polarization of the CMB. • CMB Polarization mission • Currently being studied.