Supernovae and the Mystery of Dark Energy

www.astro.uvic.ca/~pritchetwww.astro.uvic.ca/~pritchet

Supernovae and the Mystery of Supernovae and the Mystery of Dark EnergyDark Energy

Chris PritchetU. Victoria


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


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 …”


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


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


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)


SupernovaeSupernovae


July 5th, 1054AD

Chaco Canyon, NM


Crab Nebula and Pulsar


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?


Type Ia SupernovaeType Ia SupernovaeStandard candles


(Hubble Space Telescope, NASA)

Supernova Supernova CosmologyCosmology


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


Matter and Energy in the Universe – A


““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


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


CFHT Supernova CFHT Supernova Legacy Survey Legacy Survey (SNLS)(SNLS)





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


Telescope Aperture vs. Focal Plane Area

total CCD area [Megapix]

total area in 3m+ telescopes [m2]


““Size matters Size matters …”…” Anon.

MegaCam – 1 deg x 1 degMegaCam – 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 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 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)


~1000 since Aug 2003!~1000 since Aug 2003!

Detections

04D2ca 04D2ca z=0.83 Mar 10z=0.83 Mar 10

ACSACS


June 2003 (c030622-07)

z=0.281 SN Ia


z’ as well


Spectroscopy

CFHT Gemini-N


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


GeminiGemini Acquisition image : 300s in i

HostSN

Example i(AB)=24.0

45”


Raw Frame (full)

NOD A

NOD B

Illum

inate

dS

litS

hu

ffled

imag

e

CCD1 CCD2 CCD3Spectral directionS

pati

al


Combined 2 x 4 frames (mosiaced)

SN


N(z) to July 2005 (N≈200)


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(


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


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!


JDEM/SNAP/…


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!


More SNLS information

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

http://legacy.astro.utoronto.ca/



http://www.cfht.hawaii.snls/


Documents

Supernovae and the Mystery of Dark Energy