Supernovae and the Mystery of Dark Energy

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Supernovae and the Mystery of Dark Energy

• Chris Pritchet
• U. Victoria

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Golden Moments in Cosmology General Relativity
(1915)
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Golden Moments in Cosmology Expansion of the
Universe
Einsteins greatest blunder
Hubble 1929 v Ho d
Edwin Hubble - Gail Christianson
v
d
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Cosmology A Search for 2 Numbers?

• Hubble constant - Ho gives age and size of the
  Universe
• Omega - O matter and energy density
  ultimate fate of the Universe

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The Hubble Diagram (m vs z)(what Hubble actually
did)
Universe eventually collapses
Universe expands forever
Standard candle
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gt400 nights of Palomar 200 time!
evolution (mass and age)
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Supernovae
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July 5th, 1054AD
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Crab Nebula and Pulsar
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Why are Supernovae Interesting?

• L1010Lsun LMW
• Source of almost all heavy elements (12C - )
• Neutrinos, gravitational waves,
• Great physics!
• Extinction events?

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Type Ia Supernovae
Standard candles
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Supernova Cosmology

• (Hubble Space Telescope, NASA)

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Supernovae and Dark Energy
Riess et al. 1998 Perlmutter et al. 1999

• Supernovae fainter than expected
• Universe is accelerating, not decelerating!
• Universe dominated by dark energy
• Large scale repulsive force
• Constant density
• Einstein was right!

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Matter and Energy in the Universe A
Strange Brew
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Rocky Horror Show Tucson 2004
Our theoretical understanding is so limited
right now - Rocky Kolb, Tucson, Mar 2004
not understood sufficiently to answer the
basic questions - Rocky Kolb, Tucson, Mar 2004
On a good day I can think of 3 or 4 plausible
candidates for dark matter. The same cannot be
said for dark energy. - Rocky Kolb, Tucson, Mar
2004
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Why did I decide to do astronomy?
big.fits
Greatest discovery in cosmology since Hubble 1927!
too big.fits
biases.fits
excessive.fits
Really big.fits
Flats.fits
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CFHT Supernova Legacy Survey (SNLS)
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Canada-France-Hawaii Telescope (Canada 42.5)
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Telescope Aperture vs. Focal Plane Area
total area in 3m telescopes m2
total CCD area Megapix
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MegaCam 1 deg x 1 deg
Size matters
Anon.
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MegaCam at CFHT

• 1 deg x 1 deg field
• 40 x (2048 x 4612) chips ( 400Megapixels)
• good blue response

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French Group Reynald Pain, Pierre
Astier, Julien Guy, Nicolas Regnault, Jim Rich,
Stephane Basa, Dominique Fouchez
Toronto Group Ray Carlberg, Mark Sullivan, Andy
Howell, Kathy Perrett, Alex Conley
UK Gemini PI Isobel Hook Justin Bronder,
Richard McMahon, Nic Walton
USA LBL Saul Perlmutter CIT Richard Ellis
Plus Many students and associate members
throughout the world
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CFHT Legacy Survey

• 470 nights (dark-grey)
• over 5 years (2003-2008)

• Supernova Legacy Survey (SNLS)
• 202 nights over 5 years
• four 1 deg² fields (0226-04, 100002, 141953,
  2215-18)

• 4 filters, obs every 3-4 days, queue scheduling
• depth igt24.5 (S/N8, 1 hr) r gt 28 in final
  stacked image
• 700 SNeIa over 5 yrs
• Goal value of w, nature of dark energy

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Detections
1000 since Aug 2003!
04D2ca z0.83 Mar 10
ACS
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June 2003 (c030622-07)
z0.281 SN Ia
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z as well
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• Spectroscopy

CFHT
Gemini-N
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Follow-up Spectroscopy
Keck (8 nights/yr)
Gemini N S (120 hr/yr) Canada/UK/US
More 8-10m time than CFHT time
VLT (120 hr/yr) France/UK
Magellan (15 nights/ yr) Carnegie /Toronto
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Gemini Acquisition image 300s in i
Example i(AB)24.0
Host SN
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Raw Frame (full)
Illuminated Slit
NOD A
Shuffled image
NOD B
CCD1
CCD2
CCD3
Spatial
Spectral direction
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Combined 2 x 4 frames (mosiaced)
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N(z) to July 2005 (N200)
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First Year Cosmology (Astier et al.
2005,astro-ph/0510447)
Intrinsic disp. 0.13 0.02 Low-z 0.15
0.02 SNLS 0.12 0.02
First year results (72 SNe Ia) consistent with an
accelerating Universe OM0.263 in a flat universe
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w -1.02 0.09
Astier et al 2006

• Dark Energy acts exactly like Einsteins
  cosmological constant
• SNLS 1st Year Results already the best
  available!

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Future

• 500-700 supernovae by 2008
• Greatly improved limits on how dark energy
  differs from a pure cosmological constant
• First measurements of how dark energy changes
  with time
• Constraints on nature of dark energy
• Amazing stuff on nature of supernovae!

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JDEM/SNAP/
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Conclusions

• Dark Energy is not to be confused with dark
  matter.
• Dark Energy is a major (70) constituent of the
  Universe
• This is probably the most amazing discovery in
  cosmology since the discovery of the expansion of
  the Universe.
• Dark energy resembles pure Einstein cosmological
  constant.
• Currently SNLS (Canada-France) is leading the
  world in probing dark energy
• Future prospects are bright!

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More SNLS information

• http//legacy.astro.utoronto.ca/ - database
• www.cfht.hawaii.SNLS people, papers,

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