rencontre de monriond 2006 snls 1st year cosmological results snls : cosmological results from the...
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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
Rencontre de Monriond 2006 SNLS 1st year cosmological results
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
Rencontre de Monriond 2006 SNLS 1st year cosmological results
Deep homogenous and complete SNIa observations
– Detection– Photometry– Spectroscopy
Rencontre de Monriond 2006 SNLS 1st year cosmological results
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
Rencontre de Monriond 2006 SNLS 1st year cosmological results
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
- =
Rencontre de Monriond 2006 SNLS 1st year cosmological results
Photometry :deep and well sampled lightcurves
• Rolling search method : same field every 4 days = automatic follow up (and down!)
Rencontre de Monriond 2006 SNLS 1st year cosmological results
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)
Rencontre de Monriond 2006 SNLS 1st year cosmological results
Spectroscopy
• Spectrocopy : 8m - class– VLT + FORS1
– Gemini + GMOS
– Others : KECK + LRIS
250H/year of spectro250H/year of photo
Rencontre de Monriond 2006 SNLS 1st year cosmological results
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
Rencontre de Monriond 2006 SNLS 1st year cosmological results
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 …
Rencontre de Monriond 2006 SNLS 1st year cosmological results
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)
Rencontre de Monriond 2006 SNLS 1st year cosmological results
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
Rencontre de Monriond 2006 SNLS 1st year cosmological results
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
Rencontre de Monriond 2006 SNLS 1st year cosmological results
Differential Photometry: Results
• Photometry close to optimal (only 15% worse than photon statistics)
• Lightcurve points : flux with errors (full covariance matrix)
Rencontre de Monriond 2006 SNLS 1st year cosmological results
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’)
Rencontre de Monriond 2006 SNLS 1st year cosmological results
Hubble diagram and cosmology
– Lightcurve modelling , fitting and luminosity distance– Hubble diagram and cosmological parameter fitting– Full cosmological parameter error estimation
Rencontre de Monriond 2006 SNLS 1st year cosmological results
Lightcurve fitting with SALT method
• 2 parameters describe the variability of SNIa lightcurves, but the luminosity at max : s and c (‘stretch and color’)
Rencontre de Monriond 2006 SNLS 1st year cosmological results
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 :
Rencontre de Monriond 2006 SNLS 1st year cosmological results
Hubble diagram
• 44 low z + 71 SNLS Supernovae
Rencontre de Monriond 2006 SNLS 1st year cosmological results
SNLS 2.5 year
Hubble diagram : Coming soon ...
Rencontre de Monriond 2006 SNLS 1st year cosmological results
Cosmological parameter fits
BAO: Baryonic Acoustic OscillationEisentein 2005
Rencontre de Monriond 2006 SNLS 1st year cosmological results
Systematic uncertainties
• Possible sources :– Calibration and photometry
– Evolution
– Malmquist bias
– Contamination
– Gray dust
– Lensing
Rencontre de Monriond 2006 SNLS 1st year cosmological results
Calibration
• 1% on zero points :
Rencontre de Monriond 2006 SNLS 1st year cosmological results
Evolution: Comparison Low/High Z
• ?
No sizeable evolution !
Stretch color
Rencontre de Monriond 2006 SNLS 1st year cosmological results
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
Rencontre de Monriond 2006 SNLS 1st year cosmological results
Summary of systematic uncertainties
Rencontre de Monriond 2006 SNLS 1st year cosmological results
Final result
Statistical error is still dominant …
Rencontre de Monriond 2006 SNLS 1st year cosmological results
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.
– …