2. April 17, 2001Lynn Cominsky - Cosmology A3501 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

3. April 17, 2001Lynn Cominsky - Cosmology A3502 Group 10 Brian Berryessa Charity Haas Andrew McFarland Jessica Rapin John Wilczak?

4. April 17, 2001Lynn Cominsky - Cosmology A3503 Group 10

5. April 17, 2001Lynn Cominsky - Cosmology A3504 Background Radiation Lecture 10

6. April 17, 2001Lynn Cominsky - Cosmology A3505 Big Bang Timeline We are here Today’s lecture

7. April 17, 2001Lynn Cominsky - Cosmology A3506 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!

8. April 17, 2001Lynn Cominsky - Cosmology A3507 Where is the CMBR? Map of redshift vs. time after Big Bang CMBR Z=1000 Universe has expanded and cooled down by 1+z (about 1000) since the photons last scattered off the CMBR

9. April 17, 2001Lynn Cominsky - Cosmology A3508 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

10. April 17, 2001Lynn Cominsky - Cosmology A3509 COBE launch movie COsmic Background Explorer Launched 11/18/89 into polar orbit

11. April 17, 2001Lynn Cominsky - Cosmology A35010 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

12. April 17, 2001Lynn Cominsky - Cosmology A35011 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

13. April 17, 2001Lynn Cominsky - Cosmology A35012 COBE data/FIRAS Far InfraRed Absolute Spectrophotometer

14. April 17, 2001Lynn Cominsky - Cosmology A35013 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

15. April 17, 2001Lynn Cominsky - Cosmology A35014 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 10 6 times smaller and hotter than it is now. Photons continued to scatter until the Universe was 10 -3 its present size

16. April 17, 2001Lynn Cominsky - Cosmology A35015 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”

17. April 17, 2001Lynn Cominsky - Cosmology A35016 COBE data/DMR Dipole due to movement of Solar System warm cool

18. April 17, 2001Lynn Cominsky - Cosmology A35017 COBE data/DMR Dipole removed to show “wrinkles”

19. April 17, 2001Lynn Cominsky - Cosmology A35018 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)

20. April 17, 2001Lynn Cominsky - Cosmology A35019 CMBR Fluctuations COBE measures the angular fluctuations on large scales, down to about L=16

21. April 17, 2001Lynn Cominsky - Cosmology A35020 CMBR Fluctuations Determining the spectrum of fluctuations in the CMBR can directly differentiate between models of the Universe Angular size of fluctuation How much power there is

22. April 17, 2001Lynn Cominsky - Cosmology A35021 CMBR Fluctuations Current data favor a peak near L Eff = 210 This is consistent with the sCDM (standard Cold Dark Matter) and  CDM models (CDM + cosmological constant) Both describe a flat (  =1) Universe

23. April 17, 2001Lynn Cominsky - Cosmology A35022 CMBR Fluctuations For a given model (e.g., sCDM) the fluctuation spectrum can also be used to directly determine the Hubble constant

24. April 17, 2001Lynn Cominsky - Cosmology A35023 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

25. April 17, 2001Lynn Cominsky - Cosmology A35024 BOOMERanG Photos from 1998 flight in Antarctica

26. April 17, 2001Lynn Cominsky - Cosmology A35025 BOOMERanG vs. COBE 1800 square degrees of sky -300  K +300  K moon

27. April 17, 2001Lynn Cominsky - Cosmology A35026 BOOMERanG 1998 Data What the fluctuations would look like to scale on the real sky above the BOOMERanG balloon launch facilities

28. April 17, 2001Lynn Cominsky - Cosmology A35027 BOOMERanG 1998 Data What the fluctuations would look like for open, flat and closed universe models Closed: larger structures Open: smaller structures

29. April 17, 2001Lynn Cominsky - Cosmology A35028 BOOMERanG 1998 Data Peak at 1 o indicates presence of both baryonic and non- baryonic matter Second peak tells you how much of each

30. April 17, 2001Lynn Cominsky - Cosmology A35029 BOOMERanG vs. Supernovae Flat universe is best fit to BOOMERanG data Overlap with supernova data indicates cosmological constant > 0 matter

31. April 17, 2001Lynn Cominsky - Cosmology A35030 MAXIMA Millimeter Anisotrop eXperiment IMaging Array – launched 6/15/99

32. April 17, 2001Lynn Cominsky - Cosmology A35031 MAXIMA 10 arc minute resolution 150 GHz and 240 GHz 15,000 pixels Smoothed image

33. April 17, 2001Lynn Cominsky - Cosmology A35032 BOOMERanG and MAXIMA Results 0.85<  tot  <1.25 Supports cosmological constant   =0.6 (accelerating Universe), since  M is only about 0.2-0.4 (including dark matter)

34. April 17, 2001Lynn Cominsky - Cosmology A35033 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

35. April 17, 2001Lynn Cominsky - Cosmology A35034 X-ray Background ROSAT 0.75 keV map Shows smooth blue background plus bright superbubble ring at D=150 pc with R= ~100 pc

36. April 17, 2001Lynn Cominsky - Cosmology A35035 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

37. April 17, 2001Lynn Cominsky - Cosmology A35036 CGRO/EGRET data 30-40% of gamma-ray background is unresolved and extragalactic in origin

38. April 17, 2001Lynn Cominsky - Cosmology A35037 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?

39. April 17, 2001Lynn Cominsky - Cosmology A35038 Microwave Anistropy Probe 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. 7 o for COBE) and fill in the fluctuation plot 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?

40. April 17, 2001Lynn Cominsky - Cosmology A35039 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

41. April 17, 2001Lynn Cominsky - Cosmology A35040 Microwave Anistropy Probe

42. April 17, 2001Lynn Cominsky - Cosmology A35041 Microwave Anistropy Probe Dipole as predicted byi MAP simulations Fluctuations as predicted by MAP simulations

43. April 17, 2001Lynn Cominsky - Cosmology A35042 MAP limits MAP will have error bars as shown in yellow, improving data until about L eff = l000

44. April 17, 2001Lynn Cominsky - Cosmology A35043 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 L eff from 600 to 2000

45. April 17, 2001Lynn Cominsky - Cosmology A35044 Planck COBE vs. Planck What Planck will see

46. April 17, 2001Lynn Cominsky - Cosmology A35045 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

47. April 17, 2001Lynn Cominsky - Cosmology A35046 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/ http://astro.estec.esa.nl/SA- general/Projects/Planck/ BOOMERanG http://www.physics.ucsb.edu/~boomerang/

48. April 17, 2001Lynn Cominsky - Cosmology A35047 Web Resources Ned Wright’s CMBR pages http://www.astro.ucla.edu/~wright/CMB-DT.html Bell Labs Cosmology Archives http://www.bell- labs.com/project/feature/archives/cosmology/http://www.bell- labs.com/project/feature/archives/cosmology/ GLAST project outreach web site http://www-glast.sonoma.edu http://w MAXIMA experiment http://cfpa.berkeley.edu/group/cmb/ http://cfpa.berkeley.edu/group/cmb/ Chandra X-ray Background Results http://chandra.harvard.edu/press/00_releases/press_0114 00bg.html

49. April 17, 2001Lynn Cominsky - Cosmology A35048 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