Supernovae and the Mystery of Dark Energy Chris Pritchet U. Victoria

Golden Moments in Cosmology : General Relativity (1915) large-scale repulsive force ρ=const large-scale repulsive force, ρ=const

v = H o d Hubble 1929: v = H o d v d Golden Moments in Cosmology: Expansion of the Universe “Edwin Hubble …” - Gail Christianson “… Einstein’s greatest blunder …”

Cosmology – A Search for 2 Numbers?  Hubble constant - Ho – gives age and size of the Universe  Omega - Ω – matter and energy density – ultimate fate of the Universe

The Hubble Diagram (m vs z) (what Hubble actually did) faintbright nearby distant V [km/s] Ω=1 Ω<1 Ω>1 Standard candle Universe expands forever Universe eventually collapses

Gunn and Oke 1975 “… although the heterogeneity of the sample makes conclusions about cosmology slightly suspect.” -2 < Ω <0 +2 < Ω < +4 Kristian, Sandage and Westphal 1978 >400 nights of Palomar 200” time! evolution (mass and age)

Supernovae

July 5 th, 1054AD Chaco Canyon, NM

Crab Nebula and Pulsar

Why are Supernovae Interesting?  L~10 10 L sun ~L MW  Source of almost all heavy elements ( 12 C - …)  Neutrinos, gravitational waves, …  Great physics!  Extinction events?

Type Ia Supernovae Standard candles

(Hubble Space Telescope, NASA) Supernova Cosmology

Supernovae and Dark Energy  Supernovae fainter than expected  Universe is accelerating, not decelerating!  Universe dominated by dark energy  Large scale repulsive force  Constant density  Einstein was right! Riess et al Perlmutter et al. 1999

Matter and Energy in the Universe – A

“On a good day I can think of 3 or 4 plausible candidates for dark matter. The same cannot be said for dark energy.” “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 “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 Rocky Horror Show – Tucson 2004

Why did I decide to do astronomy? excessive.fits big.fits Really big.fits too big.fits Flats.fits biases.fits

CFHT Supernova Legacy Survey (SNLS)

Canada-France-Hawaii Telescope Canada-France-Hawaii Telescope (Canada 42.5%)

Telescope Aperture vs. Focal Plane Area total CCD area [Megapix] total area in 3m+ telescopes [m 2 ]

“Size matters …” Anon. MegaCam – 1 deg x 1 deg

MegaCam at CFHT  1 deg x 1 deg field  40 x (2048 x 4612) chips (~ 400Megapixels)  good blue response “Size matters …” Anon.

Toronto Group Ray Carlberg, Mark Sullivan, Andy Howell, Kathy Perrett, Alex Conley French Group Reynald Pain, Pierre Astier, Julien Guy, Nicolas Regnault, Jim Rich, Stephane Basa, Dominique Fouchez UK Gemini PI: Isobel Hook + Justin Bronder, Richard McMahon, Nic Walton Victoria Group Chris Pritchet, Don Neill, Dave Balam, Eric Hsiao, Melissa Graham USA LBL: Saul Perlmutter CIT: Richard Ellis Plus: Many students and associate members throughout the world

CFHT Legacy Survey  Supernova Legacy Survey (SNLS)  202 nights over 5 years  four 1 deg² fields ( , , , )  4 filters, obs every 3-4 days, queue scheduling  depth i’>24.5 (S/N=8, 1 hr); r’ > 28 in final stacked image  ~700 SNeIa over 5 yrs Goal: value of “w”, nature of dark energy Goal: value of “w”, nature of dark energy 470 nights (dark-grey) over 5 years ( )

~1000 since Aug 2003! Detections 04D2ca z=0.83 Mar 10 ACS

June 2003 (c ) z=0.281 SN Ia

z’ as well

Spectroscopy CFHTGemini-N

Follow-up Spectroscopy Keck (~8 nights/yr) Magellan (15 nights/ yr) Carnegie /Toronto: VLT (120 hr/yr) France/UK: Gemini N & S (120 hr/yr) Canada/UK/US More 8-10m time than CFHT time

Gemini Gemini Acquisition image : 300s in i Host SN Example i(AB)= ”

Raw Frame (full) NOD A NOD B Illuminated Slit Shuffled image CCD1CCD2CCD3 Spectral direction Spatial

Combined 2 x 4 frames (mosiaced) SN

N(z) to July 2005 (N≈200)

First Year Cosmology (Astier et al. 2005, astro-ph/ ) First year results (72 SNe Ia) consistent with an accelerating Universe: Ω M =0.263 in a flat universe Intrinsic disp.: 0.13 ± 0.02 Low-z: 0.15 ±0.02 SNLS: 0.12 ± 0.02

w = ± 0.09 w = ± 0.09  Dark Energy acts exactly like Einstein’s cosmological constant  SNLS 1st Year Results – already the best available! Astier et al 2006

Future  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!

JDEM/SNAP/…

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!

More SNLS information   - database   – people, papers, …