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Answer to last week’s Question

Answer to last week’s Question. How do we know that the Milky Way is at the outer edge of the Virgo cluster? A) We can see the center of the Virgo cluster B) We can measure our velocity with respect to the Virgo cluster and we are heading towards it

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Answer to last week’s Question

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  1. Answer to last week’s Question How do we know that the Milky Way is at the outer edge of the Virgo cluster? A) We can see the center of the Virgo cluster B) We can measure our velocity with respect to the Virgo cluster and we are heading towards it C) We can measure our velocity with respect to the Virgo cluster and we are heading away from it D) We can see the edges of the cluster B Lynn Cominsky - Cosmology A350

  2. Group 10 • Brian Berryessa • Charity Haas • Andrew McFarland • Jessica Rapin • John Wilczak? Lynn Cominsky - Cosmology A350

  3. Group 10 A round of applause for Group 10! Lynn Cominsky - Cosmology A350

  4. Background Radiation Lecture 10 Lynn Cominsky - Cosmology A350

  5. Today’s lecture Big Bang Timeline We are here Lynn Cominsky - Cosmology A350

  6. Cosmic Microwave Background • Discovered in 1965 by Arno Penzias and Robert Wilson who were working at Bell Labs • Clinched the hot big bang theory Excess noise in horned antennae was not due to pigeon dung! Lynn Cominsky - Cosmology A350

  7. CMBR Z=1000 Where is the CMBR? • Map of redshift vs. time after Big Bang Universe has expanded and cooled down by 1+z (about 1000) since the photons last scattered off the CMBR Lynn Cominsky - Cosmology A350

  8. CMBR • Photons in CMBR come from surface of last scattering – where they stop interacting with matter and travel freely through space • CMBR photons emanate from a cosmic photosphere – like the surface of the Sun – except that we inside it looking out • The cosmic photosphere has a temperature which characterizes the radiation that is emitted • It has cooled since it was formed by more than 1000 to 2.73 degrees K Lynn Cominsky - Cosmology A350

  9. COBE launch movie • COsmic Background Explorer • Launched 11/18/89 into polar orbit Lynn Cominsky - Cosmology A350

  10. COBE • 3 instruments: FIRAS, DMR and DIRBE • Cryogens ran out on 9/ 21/ 90 ending observations by FIRAS and longer wavelengths of DIRBE • DMR and the shorter wavelengths of DIRBE operated until 11/23/93 Lynn Cominsky - Cosmology A350

  11. COBE data/DIRBE • Diffuse InfraRed Background Experiment • IR background is produced by dust warmed by all the stars that have existed since the beginning of time • Limit to energy produced by all stars in the Universe Lynn Cominsky - Cosmology A350

  12. COBE data/FIRAS • Far InfraRed Absolute Spectrophotometer Lynn Cominsky - Cosmology A350

  13. COBE data/FIRAS • FIRAS results show that 99.994% of the radiant energy of the Universe was released within the first year after the Big Bang • Data match the Big Bang predictions so exactly that the error bars are within the curve itself Residuals from a 2.728 (+/- 0.004) degree Kelvin blackbody Lynn Cominsky - Cosmology A350

  14. COBE data/FIRAS • The CMBR is described by the most perfect blackbody spectrum ever measured • Blackbody spectra are produced when material is thick and dense, so that photons must scatter many times before they escape • The photons must therefore have been emitted from dark, thick matter at a much earlier time • The CMBR energy was emitted when the Universe was 106 times smaller and hotter than it is now. Photons continued to scatter until the Universe was 10-3 its present size Lynn Cominsky - Cosmology A350

  15. COBE DMR • Differential Microwave Radiometer • 3 different wavelengths • 2 antennae for each wavelength, 7 degree beam • Pointed 60 degrees apart DMR work featured in George Smoot’s “Wrinkles in Time” Lynn Cominsky - Cosmology A350

  16. warm cool COBE data/DMR • Dipole due to movement of Solar System Lynn Cominsky - Cosmology A350

  17. COBE data/DMR • Dipole removed to show “wrinkles” Lynn Cominsky - Cosmology A350

  18. COBE data/DMR • Fluctuations in CMB seen by DMR are at the level of one part in 100,000 Blue spots mean greater density Red spots mean lesser density (in the early Universe) Lynn Cominsky - Cosmology A350

  19. CMBR Fluctuations • COBE measures the angular fluctuations on large scales, down to about L=16 Lynn Cominsky - Cosmology A350

  20. How much power there is Angular size of fluctuation CMBR Fluctuations • Determining the spectrum of fluctuations in the CMBR can directly differentiate between models of the Universe Lynn Cominsky - Cosmology A350

  21. CMBR Fluctuations • Current data favor a peak near LEff = 210 • This is consistent with the sCDM (standard Cold Dark Matter) and LCDM models (CDM + cosmological constant) • Both describe a flat (W=1) Universe Lynn Cominsky - Cosmology A350

  22. CMBR Fluctuations • For a given model (e.g., sCDM) the fluctuation spectrum can also be used to directly determine the Hubble constant Lynn Cominsky - Cosmology A350

  23. BOOMERanG • Balloon Observations Of Millimeter Extragalactic Radiation and Geophysics • 12 - 20 arc min resolution – about 35 times better than COBE • Two flights: 1998/99 (10 days) and 1999/00 • Sensitive to temperature differences as small as 0.0001 degrees C • Imaged 2.5% of entire sky Lynn Cominsky - Cosmology A350

  24. BOOMERanG Photos from 1998 flight in Antarctica Lynn Cominsky - Cosmology A350

  25. moon -300 mK +300 mK BOOMERanG vs. COBE 1800 square degrees of sky Lynn Cominsky - Cosmology A350

  26. BOOMERanG 1998 Data • What the fluctuations would look like to scale on the real sky above the BOOMERanG balloon launch facilities Lynn Cominsky - Cosmology A350

  27. BOOMERanG 1998 Data • What the fluctuations would look like for open, flat and closed universe models • Closed: larger structures • Open: smaller structures Lynn Cominsky - Cosmology A350

  28. BOOMERanG 1998 Data • Peak at 1o indicates presence of both baryonic and non-baryonic matter • Second peak tells you how much of each Lynn Cominsky - Cosmology A350

  29. matter BOOMERanG vs. Supernovae • Flat universe is best fit to BOOMERanG data • Overlap with supernova data indicates cosmological constant > 0 Lynn Cominsky - Cosmology A350

  30. MAXIMA • Millimeter Anisotrop eXperiment IMaging Array – launched 6/15/99 Lynn Cominsky - Cosmology A350

  31. MAXIMA • 10 arc minute resolution • 150 GHz and 240 GHz • 15,000 pixels • Smoothed image Lynn Cominsky - Cosmology A350

  32. BOOMERanG and MAXIMA Results • 0.85< Wtot<1.25 • Supports cosmological constant WL =0.6 (accelerating Universe), since WM is only about 0.2-0.4 (including dark matter) The Universe is FLAT! Lynn Cominsky - Cosmology A350

  33. X-ray Background • Discovered over 35 years ago in rocket flights • Early theories explained the X-ray background as a diffuse, hot gas which filled the Universe • Data from Einstein Observatory showed about 50% of the background could be due to quasars • ROSAT data explained about 60% of the 1-2 keV X-ray background with quasars • However flux and energy spectra did not add up correctly if the background was all quasars Chandra to the rescue! Lynn Cominsky - Cosmology A350

  34. X-ray Background • ROSAT 0.75 keV map Shows smooth blue background plus bright superbubble ring at D=150 pc with R= ~100 pc Lynn Cominsky - Cosmology A350

  35. Chandra data • At least 80% of X-ray background is made of discrete sources including two new types: • Very distant galaxies with faint black holes • Bright black holes without visible galaxies Results were from comparing Chandra data to deep optical surveys from Keck Lynn Cominsky - Cosmology A350

  36. CGRO/EGRET data • 30-40% of gamma-ray background is unresolved and extragalactic in origin Lynn Cominsky - Cosmology A350

  37. What are the next questions? • What is the distribution of sizes of the fluctuations in the Cosmic Microwave Background? • What do the fluctuations tell us about the dark matter? About the Hubble constant? • Have we really seen enough objects to make up the entire X-ray background? • Is the extra-galactic gamma-ray background similar to the X-ray background? Lynn Cominsky - Cosmology A350

  38. Microwave Anistropy Probe How old is the Universe? How fast is it expanding? Is the Universe infinite? Is there really a cosmological constant? When did the first stars form? What is the origin of structure in the Universe? • Selected by NASA in 1996 • Will be launched in Fall 2000 to L2 • Will measure fluctuations in CMBR on a scale of 0.2 - 1 degrees (vs. 7o for COBE) and fill in the fluctuation plot Lynn Cominsky - Cosmology A350

  39. Microwave Anistropy Probe • L2 is one of the 3 unstable points in the Earth-Sun binary system • Another body can orbit at this point at a fixed distance from the Earth and the Sun with corrections every 23 days Lynn Cominsky - Cosmology A350

  40. Microwave Anistropy Probe Lynn Cominsky - Cosmology A350

  41. Dipole as predicted byi MAP simulations Fluctuations as predicted by MAP simulations Microwave Anistropy Probe Lynn Cominsky - Cosmology A350

  42. MAP limits • MAP will have error bars as shown in yellow, improving data until about Leff = l000 Lynn Cominsky - Cosmology A350

  43. Planck • ESA mission to be launched in 2007 • Will measure entire sky to 10’ to 2 parts per million • Will give better information than MAP for Leff from 600 to 2000 Lynn Cominsky - Cosmology A350

  44. COBE vs. Planck What Planck will see Planck Lynn Cominsky - Cosmology A350

  45. Gamma-ray Background • Simulated sky as seen by GLAST after 1 year of observation • Key goal to determine if extra-galactic gamma-radiation is from discrete sources Lynn Cominsky - Cosmology A350

  46. Web Resources • Cosmic Background Explorer http://space.gsfc.nasa.gov/astro/cobe/cobe_home.html • Microwave Anistropy Probe http://map.gsfc.nasa.gov • Planck mission http://astro.estec.esa.nl/SA-general/Projects/Planck/ • BOOMERanG http://www.physics.ucsb.edu/~boomerang/ Lynn Cominsky - Cosmology A350

  47. Web Resources • Ned Wright’s CMBR pageshttp://www.astro.ucla.edu/~wright/CMB-DT.html • Bell Labs Cosmology Archiveshttp://www.bell-labs.com/project/feature/archives/cosmology/ • GLAST project outreach web site http://www-glast.sonoma.edu • MAXIMA experimenthttp://cfpa.berkeley.edu/group/cmb/ • Chandra X-ray Background Results http://chandra.harvard.edu/press/00_releases/press_011400bg.html Lynn Cominsky - Cosmology A350

  48. Question of the Week Is there background radiation at all wavelengths? A) No, only at microwave wavelengths B) No, only at microwave, X-ray and gamma-ray wavelengths C) Yes and it is the same intensity at all wavelengths D) Yes but the radiation is different intensities at different wavelengths Lynn Cominsky - Cosmology A350

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