Supernovae and the Mystery of Dark Energy
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Transcript of Supernovae and the Mystery of Dark Energy
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Supernovae and the Mystery of Supernovae and the Mystery of Dark EnergyDark Energy
Chris PritchetU. Victoria
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Golden Moments in Cosmology :Golden Moments in Cosmology :General Relativity (1915)General Relativity (1915)
T
c
GG
4
8
gTc
GG
4
8
large-scale repulsive forcelarge-scale repulsive force, ρρ=const=const
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Hubble 1929: v = Hv = Hoo d d
v
d
Golden Moments in Cosmology:Golden Moments in Cosmology: Expansion of the UniverseExpansion of the Universe
“Edwin Hubble …” - Gail Christianson
“… “… Einstein’s greatest blunder …”Einstein’s greatest blunder …”
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Cosmology – A Search for 2 Cosmology – A Search for 2 Numbers?Numbers?
Hubble constant - Ho – gives age and size of the Universe
Omega - Ω – matter and energy density – ultimate fate of the Universe
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The Hubble Diagram (m vs z)(what Hubble actually did)
faintbrightnearby
distant
V [
km/s
]
Ω=1Ω<1
Ω>1
Standard candle
Universe expands forever
Universe eventually collapses
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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 >400 nights of Palomar of Palomar 200” time!200” time!
evolution (mass and age)
evolution (mass and age)
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SupernovaeSupernovae
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July 5th, 1054AD
Chaco Canyon, NM
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Crab Nebula and Pulsar
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Why are Supernovae Why are Supernovae Interesting?Interesting?
L~10L~101010LLsun sun ~L~LMWMW Source of almost all heavy elements (12C - …) Neutrinos, gravitational waves, … Great physics! Extinction events?
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Type Ia SupernovaeType Ia SupernovaeStandard candles
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(Hubble Space Telescope, NASA)
Supernova Supernova CosmologyCosmology
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Supernovae and Dark EnergySupernovae 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. 1998Riess et al. 1998Perlmutter et al. 1999Perlmutter et al. 1999
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Matter and Energy in the Universe – A
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““On a good day I can think of 3 or 4 On a good day I can think of 3 or 4 plausible candidates for dark plausible candidates for dark matter. The same cannot be said matter. The same cannot be said for dark energy.”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
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Why did I Why did I decide to decide to do do astronomy?astronomy?
Why did I Why did I decide to decide to do do astronomy?astronomy?
excessive.fits
big.fits
Really big.fits
too big.fits
Flats.fits
biases.fits
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CFHT Supernova CFHT Supernova Legacy Survey Legacy Survey (SNLS)(SNLS)
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Canada-France-Hawaii Canada-France-Hawaii Telescope Telescope (Canada 42.5%)
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Telescope Aperture vs. Focal Plane Area
total CCD area [Megapix]
total area in 3m+ telescopes [m2]
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““Size matters Size matters …”…” Anon.
MegaCam – 1 deg x 1 degMegaCam – 1 deg x 1 deg
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MegaCam at CFHT
1 deg x 1 deg field 40 x (2048 x 4612) chips (~ 400Megapixels) good blue response
““Size matters Size matters …”…” Anon.
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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
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CFHT Legacy SurveyCFHT Legacy Survey
Supernova Legacy Survey (SNLS)Supernova Legacy Survey (SNLS) 202 nights over 5 years202 nights over 5 years four 1 degfour 1 deg² ² fields (0226-04, 1000+02, 1419+53, 2215-18)fields (0226-04, 1000+02, 1419+53, 2215-18)4 filters, obs every 3-4 days, 4 filters, obs every 3-4 days, queue schedulingqueue scheduling
depth i’>24.5 (S/N=8, 1 hr); r’ > 28 in final stacked imagedepth i’>24.5 (S/N=8, 1 hr); r’ > 28 in final stacked image~700 SNeIa over 5 yrs~700 SNeIa over 5 yrs
Goal: value of “w”, nature of dark energyGoal: value of “w”, nature of dark energy
470 nights (dark-grey) 470 nights (dark-grey) over 5 years (2003-2008)over 5 years (2003-2008)
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~1000 since Aug 2003!~1000 since Aug 2003!
Detections
04D2ca 04D2ca z=0.83 Mar 10z=0.83 Mar 10
ACSACS
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June 2003 (c030622-07)
z=0.281 SN Ia
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z’ as well
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Spectroscopy
CFHT Gemini-N
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Follow-up SpectroscopyFollow-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 timeMore 8-10m time than CFHT time
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GeminiGemini Acquisition image : 300s in i
HostSN
Example i(AB)=24.0
45”
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Raw Frame (full)
NOD A
NOD B
Illum
inate
dS
litS
hu
ffled
imag
e
CCD1 CCD2 CCD3Spectral directionS
pati
al
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Combined 2 x 4 frames (mosiaced)
SN
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N(z) to July 2005 (N≈200)
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First Year Cosmology First Year Cosmology (Astier et al. 2005,(Astier et al. 2005,astro-ph/0510447)astro-ph/0510447)
First year results (72 SNe Ia) consistent
with an accelerating
Universe: ΩM=0.263 in a flat universe
Intrinsic disp.: 0.13 ± 0.02Low-z: 0.15 ±0.02
SNLS: 0.12 ± 0.02
csMmBB )1(
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w = -1.02 w = -1.02 ± 0.09± 0.09
Dark Energy acts exactly like Einstein’s cosmological constant
SNLS 1st Year Results – already the best SNLS 1st Year Results – already the best available!available!
Astier et al 2006
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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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ConclusionsConclusions
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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