Supernova Legacy SurveySupernova Legacy Survey

Mark Sullivan Mark Sullivan

University of OxfordUniversity of Oxford

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

http://cfht.hawaii.edu/SNLS/http://cfht.hawaii.edu/SNLS/

Paris Group

Reynald Pain, Pierre Astier, Julien Guy, Nicolas

Regnault, Christophe Balland, Delphine Hardin,

Jim Rich, + …

Oxford

Isobel Hook (Gemini PI), Mark Sullivan, Emma

Walker

Full list of collaborators at: http://cfht.hawaii.edu/SNLS/

Victoria Group

Chris Pritchet, Dave Balam, + …

Toronto Group

Ray Carlberg, Alex Conley, Andy Howell, Kathy Perrett

The SNLS The SNLS collaborationcollaboration

Marseille Group

Stephane Basa, Dominique Fouchez

USA

LBL: Saul Perlmutter, + …

SNLS: Vital StatisticsSNLS: Vital Statistics5 year “rolling” SN survey5 year “rolling” SN survey

Goal: 500 high-z SNe to measure “w”Goal: 500 high-z SNe to measure “w”

Uses “Megacam” imager on the Uses “Megacam” imager on the CFHT; griz every 4 nights in queue CFHT; griz every 4 nights in queue scheduled modescheduled mode

Survey running for 4 yearsSurvey running for 4 years

~~350 confirmed 350 confirmed zz>0.1 SNe Ia>0.1 SNe Ia

>1500 SN detections in total>1500 SN detections in total

Largest single telescope sampleLargest single telescope sample

450-500 by survey end450-500 by survey end

Cosmology with SNe IaCosmology with SNe Ia

Distance estimator constructed in rest-frame B-band:Distance estimator constructed in rest-frame B-band:

csm BBB )1(M

““c” – B-V colour c” – B-V colour estimator corrects for estimator corrects for

extinction and/or intrinsic extinction and/or intrinsic variation via variation via ββ

s – “stretch” corrects s – “stretch” corrects for light-curve shape for light-curve shape

via via αα

“Measured” maximum light

magnitude

Standard absolute B-band magnitude

Note: for the cosmological fits is >>1 unless an “intrinsic dispersion” term is added – Note: for the cosmological fits is >>1 unless an “intrinsic dispersion” term is added – this parameterises our lack of knowledge about SNethis parameterises our lack of knowledge about SNe

DOF2

First-Year SNLS Hubble Diagram

SNLS 1SNLS 1stst year – 71 high-z SNe Ia year – 71 high-z SNe Ia

ΩM = 0.263 ± 0.042 (stat) ± 0.032 (sys)

<w>=-1.02 ± 0.09 (stat) ± 0.054 (sys) (with BAO + Flat Universe)

Astier et al. 2006Astier et al. 2006

470 citations470 citations

(297 in refereed (297 in refereed journals)journals)

SNLS 3SNLS 3rdrd year versus 1 year versus 1stst year year

Increase in SN numbers: 71 to Increase in SN numbers: 71 to ~~250250 Ability to test SN sub-samples (+ “astrophysical systematics”)Ability to test SN sub-samples (+ “astrophysical systematics”)

Optimised survey design and calibrationOptimised survey design and calibration Deeper/more frequent z’ exposures increases utility of z>0.7 SNeDeeper/more frequent z’ exposures increases utility of z>0.7 SNe 3-year monitoring of fields; better understanding of Megacam array3-year monitoring of fields; better understanding of Megacam array

Improved understanding of SN Ia propertiesImproved understanding of SN Ia properties New “k-correction” template (Hsiao et al. 2007) incorporates Ellis et New “k-correction” template (Hsiao et al. 2007) incorporates Ellis et

al. UV spectra: reduction in potential source of systematicsal. UV spectra: reduction in potential source of systematics New light curve fitting techniques exploit better understanding of SN New light curve fitting techniques exploit better understanding of SN

light curves at light curves at λλ<4000A (rms: 0.19 -> 0.16mag)<4000A (rms: 0.19 -> 0.16mag)

Hubble Hubble DiagramDiagram

~~240 distant SNe Ia240 distant SNe Ia

csm BBB )1(M

(error was 0.042 in A06)(error was 0.042 in A06)

Sullivan et al. in prep

Cosmological Constraints (Cosmological Constraints (PreliminaryPreliminary))

SNLS+BAO (No flatness) SNLS + BAO + simple WMAP + Flat

BAO BAO

SNe

SNe

WMAP-3

6-7% measure of <w>

(relaxing flatness: error in <w> goes from ~0.065 to ~0.115)

““Experimental Systematics”Experimental Systematics” Calibration, photometry, Malmquist-type effectsCalibration, photometry, Malmquist-type effects

Contamination by other SNe or peculiar SNe IaContamination by other SNe or peculiar SNe Ia Minimized by spectroscopic confirmationMinimized by spectroscopic confirmation

Non-SNe systematicsNon-SNe systematics Peculiar velocities; Hubble Bubble; Weak lensingPeculiar velocities; Hubble Bubble; Weak lensing

K-corrections and SN spectraK-corrections and SN spectra UV uncertain; “golden” redshifts; spectral evolution?UV uncertain; “golden” redshifts; spectral evolution?

Extinction/ColourExtinction/Colour Effective REffective RVV;; Intrinsic colour versus dustIntrinsic colour versus dust

Redshift evolution in the mix of SNeRedshift evolution in the mix of SNe ““Population drift” – environment?Population drift” – environment?

Evolution in SN propertiesEvolution in SN properties Light-curves/Colors/LuminositiesLight-curves/Colors/Luminosities

Potential SN Systematics in measuring w(a)Potential SN Systematics in measuring w(a)

Increasing knowledge of SN

physics“Population Evolution”

“Extinction”

Colour Colour correctioncorrection

Colour—luminosity Colour—luminosity relationship inconsistent relationship inconsistent

with MW-type dustwith MW-type dust

Best-fit: Best-fit: ββ~3~3

MW-dust: MW-dust: β≡β≡RRBB=4.1 =4.1

csm BBB )1(M

SN Colour (c)

Res

idu

al w

ith

ou

t c-

corr

ecti

on β=4.1

SN colour-colour spaceSN colour-colour space

In colour colour In colour colour space, MW-type space, MW-type extinction laws extinction laws also don’t workalso don’t work

SN U-B

SN

B

-V

Combination of dust+intrinsic?Combination of dust+intrinsic?

In colour colour In colour colour space, MW-type space, MW-type extinction laws extinction laws also don’t workalso don’t work

SN U-B

SN

B

-V

Residuals by host typeResiduals by host typeSNe in passive galaxies show a smaller scatterSNe in passive galaxies show a smaller scatter

““Intrinsic dispersion” consistent with zeroIntrinsic dispersion” consistent with zero(Does intrinsic dispersion in SNe arise from dust?)(Does intrinsic dispersion in SNe arise from dust?)

Cleaner sample: But SNe in passive galaxies are at high-z Cleaner sample: But SNe in passive galaxies are at high-z ((~~20%: two component model) + very few locally20%: two component model) + very few locally

Passive hosts Star-forming hosts

Colour correction Colour correction required in all host required in all host

types – types – with a similar with a similar ββ

Either:Either:

a)a) Passive hosts have dustPassive hosts have dust

b)b) An intrinsic relation An intrinsic relation dominates over dustdominates over dust

SN Colour (c)

Res

idu

al w

ith

ou

t c-

co

rrec

tio

nR

esid

ual

wit

ho

ut

c-c

orr

ecti

on

Passive hosts

Star-forming hosts

40 high-z SNe

180 high-z SNe

Large “local” SN surveys Large “local” SN surveys covering a wide wavelength covering a wide wavelength range (inc. near-IR) urgently range (inc. near-IR) urgently needed to disentangle thisneeded to disentangle this

Not clear what more of the Not clear what more of the same will tell us…same will tell us…

Passive Passive hostshosts

Star-forming Star-forming hostshosts

SN Ia SFR dependencies – potential evolution?SN Ia SFR dependencies – potential evolution?

170 SNLS SNe Ia170 SNLS SNe Ia

(Update from Sullivan et al. 2006; better (Update from Sullivan et al. 2006; better zeropoints, host photometry, more SNe)zeropoints, host photometry, more SNe)

SN rate versus SN rate versus host SFRhost SFR

SN stretch distributions SN stretch distributions split by galaxy star-split by galaxy star-

formation rateformation rate

SN

Ia

rate

per

un

it m

ass

SFR per unit mass

SN stretch (s)

SFRBMAt stellarIaSNR

SN mix predicted to evolve with redshiftSN mix predicted to evolve with redshift

Predicted mix Predicted mix of two of two

components components evolves evolves

stronglystrongly with with redshiftredshift

SFRBMAt stellarIaSNR

Redshift drift in stretch?

Average stretch, and thus average intrinsic brightness

of SNe Ia evolves with redshift

if stretch correction works perfectly, this will

not affect cosmology

Howell et al. 2007Howell et al. 2007

NearbyNearby

z<0.75z<0.75

z>0.75z>0.75

Full 1st year sample: solid

s<1 at z<0.4 and s>1 at z>0.4: dashed

Future SN Ia ProspectsFuture SN Ia ProspectsShort-term:Short-term:

Current constraints on <w>: <w>=-1 to Current constraints on <w>: <w>=-1 to ~6-~6-7% (stat)7% (stat)(inc. flat Universe, BAO+WMAP-3)(inc. flat Universe, BAO+WMAP-3)

At SNLS survey end statistical uncertainty will be 4-5%:At SNLS survey end statistical uncertainty will be 4-5%: 500 SNLS + 200 SDSS + larger local samples500 SNLS + 200 SDSS + larger local samples Improved external constraints (BAO, WL)Improved external constraints (BAO, WL)

Longer term:Longer term:

No evolutionary bias in cosmology detected (tests continue!)No evolutionary bias in cosmology detected (tests continue!)

SNe in passive galaxies: seem more powerful probes, but SNe in passive galaxies: seem more powerful probes, but substantially rarer (esp. at high-z)substantially rarer (esp. at high-z)

Colour corrections are the dominant uncertaintyColour corrections are the dominant uncertainty

Urgent need for z<0.1 samples with wide wavelength coverageUrgent need for z<0.1 samples with wide wavelength coverage

Not clear what the “next step” at high-z should beNot clear what the “next step” at high-z should be

Paris Group

Reynald Pain, Pierre Astier, Julien Guy, Nicolas

Regnault, Christophe Balland, Delphine Hardin,

Jim Rich, + …

Oxford

Isobel Hook (Gemini PI), Mark Sullivan, Emma

Walker

Full list of collaborators at: http://cfht.hawaii.edu/SNLS/

Victoria Group

Chris Pritchet, Dave Balam, + …

Toronto Group

Ray Carlberg, Alex Conley, Andy Howell, Kathy Perrett

The SNLS The SNLS collaborationcollaboration

Marseille Group

Stephane Basa, Dominique Fouchez

USA

LBL: Saul Perlmutter, + …