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How to know the Universe is accelerating

How to know the Universe is accelerating

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How to know the Universe is accelerating

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  1. How to know the Universe is accelerating Myung Gyoon Lee Astronomy Division, Dept of Physics and Astronomy Seoul National University, Seoul, Korea (mglee@astrog.snu.ac.kr) 2006 4.20-21, KPS Spring meeting, Phoenix

  2. Contents-Tutorial • Introduction • Method • Results • Discussion • Future

  3. Revolutions in Cosmology • 1610 Telescopic Universe • 1917 Static Model Universe, with L • 1918 our Galaxy Universe (we not at the center) • 1925 Island Universes • 1929 Expanding Universe, no L • 1965 Light Universe (CMBR = Hot Big Bang) • 1980 Inflationary Model Universe • 1984 CDM Model Universe • 1993 Seed Universe (T fluctuation)

  4. Then 1998 • 1998 Accelerating Universe, yes L!!! • 2006 Mystery of Dark Energy continues in AU

  5. Method-Concept • Equation of Motion for the expanding U • Luminosity distance(z) -- Standard candle • Varies as a function of (matter, lambda, curvature) • Standard candles look fainter in the accelerating U than in the non-acceleration U • Standard candle: Supernova Type Ia Accelerating U fainter -Luminosity Decelerating U Redshift z

  6. What are SN Ia? • In a binary system of a giant and a white dwarf, mass accretes from the giant to the white dwarf. • When m(WD)>1.4 Mo(=Chandrasekhar limit), SN Ia shows up!!!! • Progenitor: old stars •  SN type II (progenitor=massive stars - young stars) White dwarf Red giant

  7. The moment

  8. Nearest SN: 1987A (II) • 1987.2.23 • Large Magallanic Cloud • Caught its neutrinos • Type II • Progenitor - a 20 Mo supergiant

  9. Our newest SN 1604

  10. Our SN

  11. Distant SN Ia

  12. Where are SN Ia? • found in all types of galaxies • Mannucci et al(2005): much more in late types like Type IIs !!! Why?

  13. SN Ia – Standard candle • Time variation of the luminosity - Light curve • Why standard candle? • Brightness(peak) = -19.5mag(similar to a galaxy) • How good is it? • Controversial in the era of H0 game err~0.5 mag • Pretty good in the era of Lgame? (why?) err~0.1 mag

  14. Procedure • To find SN Ia at various redshift z • To measure the variation of the brightness • To apply corrections (K-correction, time dilation(z), L-width effect, etc) • To derive distance modulus (m-M) [=5logd-5] • To plot (m-M) vs z (=Hubble diagram) • To fit the data with models • To estimate M,  ,k

  15. How to find SN Ia • Probability game • Wise strategy, where and how to find? • Patience (months to years) • To compare images of different epochs and find a guest star In the past, monitoring a list of galaxies (Evans) Today, monitoring some fields for high z SNe (expensive)

  16. How to find SNe • High z SN

  17. SN Light curves • Nearby SNe (Phillips et al 1993) • The brighter, the broader • Stretch-factor correction (Perlmutter et al 1997)

  18. 1998 • SCP (Perlmuetter et al) • HzSN (Riess et al) • z(SN)<0.9

  19. 1998

  20. 1998 • M=0.3, =0.7 for k =1 Accelerating U • Would you accept it? • Other possibilities? • Dust around SN • Intergalactic dust • Evolution of SNe • ?? • How to check these? • SNe at higher z (>1) • Multi-band photometry • NIR photometry

  21. Precursors • Age problem in 1995 • Hubble age (for H0=80 km/s/Mpc) < Stellar age • No solution except for  • M~0.3 (visible 0.01, baryon 0.04) • But no constraint for  • Needed bold mind with good data based on new idea (like SCP and HzSN teams who worried a lot before announcing the results)

  22. Since 1998 • The game continues…

  23. Tough job?

  24. SCP(2003) • Knop et al (2003) • z<0.9

  25. SCP(1998-2003)

  26. SCP(2003)

  27. High-z SN Ia (2004) • Riess et al 2004

  28. Light curves of SN Ia • Riess et al 2004

  29. Hubble diagram of SN Ia • Riess et al (2004)

  30. Hubble diagram of SN Ia • Riess et al 2004

  31. Testing Others • Riess et al 2004

  32. All three today • Direct evidence: SN Ia • Indirect evidences • LSS • CMBR SN Ia LSS CMBR(WMAP)

  33. Current • Several projects going on

  34. Current-SNLS • SN Legacy Survey (SNLS)-Hook et al (Canada, France, UK, US, Sweden, Portugal) • To find 1000 Sne with CFHT MegaCam ugriz • Spectra with Keck, VLT, Gemini, Magellan • 2003.8 - 2008 • 4 Fields • Rolling search (5 epochs/month for each field)

  35. SNLS • First year data(Astier et al 2006) 71 Sne(z=0-1) • W= -1.023+/-0.090(stat)+/-0.054(sys) for flat U

  36. SNLS(2006)

  37. SNLS(2006) • M =0.271+/-0.021 • W= -1.023+/-0.090(stat)+/-0.054(sys) for flat U

  38. Current • Low-z SNe • LOTOSS(KAIT) • CFHT SNLC • Carnegie SN • ESO • SDSS SN • High-z SNe

  39. Future • New projects • SNAP (SN Acceleration Probe) • 2m space mission in 2015-2018: 2000 SNe for 3y • Putting a period of SN game? • JDEM(Joint DE mission, 2015-??) • LSST, PANSTARRS • Fast monitoring of half sky in 2010’s • Korea? • SDSS SN • Twin 6.5m in 2010’s?

  40. SNAP

  41. Future • New directions • Determining w with 1% error and check w(z) • Checking SNe (calibration using Cepheids, checking dust with IJHK • Developing other good standard candles? • SN II • Bayonic acoustic oscillation • ?? • Improving or making other tools • CMBR • Galaxies in the large scale structures • Galaxy clusters • Exotic? Quasars? GRB?

  42. Future • A lesson from Dark Matter • DM(then missing mass) was suggested in 1933 • Before 1980 DM=None • (1980-1998) >90% • (1998-now) 24% (a good way of losing mass), unknown • DE may be reduced or disappear suddenly??? • Before 1998, DE=none • (1980-now) DE=73%, UCE (unknown cosmic energy) • (after now) ???? • Well, probably not, because of CMBR and Clusters • But….