Rencontre de Monriond 2006 SNLS 1st year cosmological results SNLS : Cosmological results from the...

Rencontre de Monriond 2006 SNLS 1st year cosmological results

SNLS : Cosmological results from the first year datasetDominique Fouchez,CPPM MarseilleOn behalf of the SNLS collaboration.

Rencontres de Monriond 2006


Plan of the talk

• Deep homogenous and complete SNIa observation– Detection– Photometry : deep and well sample SN lightcurves– Spectrocopy -> identification of each SN

• Precise Measurement– Differential photometry– Calibration

• Hubble diagram and cosmology– Lightcurve modelling , fitting and luminosity distance– Hubble diagram and cosmological parameter fitting– Full cosmological parameter error estimation


Deep homogenous and complete SNIa observations

– Detection– Photometry– Spectroscopy


CFHT : 3.6 meters at Hawaii

Megacam imager of 1 sq degree

Observation of the 4 CFHTLS/DEEP 1d°2 fields in 4 colors

Photometry


Detection

• Principle of detection : same field observed every 4 days– Subtraction of each night (stacked images) on a reference image to

find individual detections then construction of Lightcurve of candidates

days

- =


Photometry :deep and well sampled lightcurves

• Rolling search method : same field every 4 days = automatic follow up (and down!)


Real Time Detection

• Need a spectroscopy a maximum of luminosity : quasi-real time detection

• 2 pipelines detect new candidatess in 24h hours time after observation

• Scanning-free-automatized detection pipeline has been set up (shapelet-neural net based detection)


Spectroscopy

• Spectrocopy : 8m - class– VLT + FORS1

– Gemini + GMOS

– Others : KECK + LRIS

250H/year of spectro250H/year of photo


March 2006 : 2.5 years of running440 spectra analysed in quasi real time

231 Ia identified with spectroscopy, ready for cosmology

The SNIa sample : Status


Digression

• In addition to SNIa sample, many variable objects, which include many SN non IA .

• This big sample make it possible to study other science topics than cosmological parameters within the SNLS photometric+spectroscopic data

They are numerous …


Other SNLS topics

Type Ia ratesMetallicity

effectsType Ia

progenitorsRedshift evolution

Cosmology with Type II SNe

SN Ia UV properties

Properties of Dust

Type Ia rise times

Epoch of cosmic deceleration

Ia explosion mechanism

Ia Intrinsic Scatter

Benetti velocity diagram

High-stretch SNe Ia diversity

Core collapse SN rate

CMAGIC

Core collapse progenitors

Improved K-corrections

SN Ib/c-GRB connection

SN Ia peak-tail ratio

Ia metallicity cutoff

Ia geometric effects

II-P risetimeIR Hubble Diagram

Type IIn - Type Ia connection

AGN/SN Ia connection

Ia pseudo-EW correlations

Host galaxy properties

Unique SNeIa high velocity

componentsSN color-color

selection

SN Luminosity distribution

Cosmic star formation history

Deflagration vs. detonation

Intrinsic Type Ia colors

Type II shock breakout

Stretch, MLCS, m15

improvements

Galactic chemical evolution

Are SNe Ia a one parameter

family?

Are there low-s SNe Ia at

high z?

Groundwork for future (JDEM,

LSST)


Precise Measurement of SNIa sample

Differential photometry

Calibration

Only the first year of data has been released and will be presented in the rest of the talk–91 Sne Ia 10 miss references

6 only have 1 band 73 usable SNIa events 2 peculiars


Differential photometry: Method

Input images +variable seeing kernel (wrt best)->Fit galaxy on a stampFit position (same in all images)Fit flux on each exposure


Differential Photometry: Results

• Photometry close to optimal (only 15% worse than photon statistics)

• Lightcurve points : flux with errors (full covariance matrix)


Photometric calibration

• Same Differential photometry is used to measure tertiary standard stars in each field

• Calibration on observed Landolt stars

• 1% zero point dispersion (except z’)


Hubble diagram and cosmology

– Lightcurve modelling , fitting and luminosity distance– Hubble diagram and cosmological parameter fitting– Full cosmological parameter error estimation


Lightcurve fitting with SALT method

• 2 parameters describe the variability of SNIa lightcurves, but the luminosity at max : s and c (‘stretch and color’)


Distance measurement

• The fitted s and c are used to correct for the ‘brighter-slower’ and ‘brighter-bluer’ behaviour

• The correction coefficients , and M have been fitted together with the cosmology on the whole lightcurve samples.

• The distance is then derived from magnitude at max in B restframe and s,c :


Hubble diagram

• 44 low z + 71 SNLS Supernovae


SNLS 2.5 year

Hubble diagram : Coming soon ...


Cosmological parameter fits

BAO: Baryonic Acoustic OscillationEisentein 2005


Systematic uncertainties

• Possible sources :– Calibration and photometry

– Evolution

– Malmquist bias

– Contamination

– Gray dust

– Lensing


Calibration

• 1% on zero points :


Evolution: Comparison Low/High Z

• ?

No sizeable evolution !

Stretch color


Malmquist bias

• ?

Selection effect (keep brightest at high z) found on the dataat same level as what expected from montecarloMax of 0.05 deviation at z=1


Summary of systematic uncertainties


Final result

Statistical error is still dominant …


Perspectives

• With full the statistics 700 SNIa expected (x10 !), the measurement will start to be ‘systematics limited’

• Improvement on main systematics errors is under study :– Calibration : z zero point ,in particular, can be improved but need

other calibrators than Landolt -> join calibration campaign with CFHT to calibrate with spectrophoto standards the DEEP fields.

– Detailled study of selection effects with huge Montecarlo dataset is underway.

– Lightcurve modelling improvements.

– …

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