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1998-2003 : Concordance model. SNe Ia prefer a non zero L. Today’s question : Cosmological Constant, Vacuum Energy or Dark Energy ?. Outline:. Cosmology with SNe Ia Why keep studying SNe Ia ? SNLS - the SuperNova Legacy Survey. Cosmology with SNe Ia.

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1998 2003 concordance model
1998-2003 : Concordance model

SNe Ia prefer

a non zero L

Today’s question :

Cosmological Constant,

Vacuum Energy


Dark Energy ?

Reynald Pain

  • Cosmology with SNe Ia
  • Why keep studying SNe Ia ?
  • SNLS - the SuperNova Legacy Survey

Reynald Pain

cosmology with sne ia
Cosmology with SNe Ia

Luminosity distance : dL(z)

SNe Ia ?

Reynald Pain

sne ia are not standard candles
SNe Ia are not standard candles

Very Luminous events

  • visible at cosmological distances

Show little intrinsic


Reynald Pain

measuring distances
Measuring distances

SNe Ia Show Light Curve Shape Relationships (similar to Cepheids P-L relation)

=> Allows to measure distances to better than 5-8% precision

Reynald Pain

sn ia spectral features
SN Ia Spectral features

From fainter to brighter…

Reynald Pain

sne ia modelisation
SNe Ia modelisation



Using radiative transfer codes, this relationship is reproduced simply by increasing the abundance of 56Ni in the explosion.

Here this is characterized by increasing the effective temperature of the atmosphere.

Reynald Pain

why keep collecting sne ia
Why keep collecting SNe Ia ?
  • Probe Dark Energy

Cosmological constant or Dark Energy ?

  • Study sytematics

- Extinction :

Host galaxy/inter-galactic « grey » dust

- Evolution :

Are nearby and distant SNe Ia alike ?

Reynald Pain

hst measured color
HST measured color
  • SCP 2003
  • +11 SN photometrically followed with HST
  • allows event by event extinction correction

Updated Hubble diagram

  • Using a low extinction subset

Reynald Pain

morphological hubble diagram
“Morphological” Hubble diagram

SCP 2002

Is there a host galaxy effect ?

Reynald Pain

sne at higher redshift goods acs survey
SNe at higher redshift (Goods/ACS survey)

Probe the deceleration era

Find Sne at z>1.2 using HST

Reynald Pain

goods acs 2004 hst supernovae
GOODS/ACS 2004: HST Supernovae

Expansion went from deceleration to acceleration

Exclude grey dust

Reynald Pain

probe dark energy
Probe Dark Energy

Cosmological constant : p=-r

Other sources : w = p/r

Source w

Matter 0

Radiation 1/3

Cosmo Cte -1

Scalar field (cte) -1

Cosmic strings -1/3

Domain wall -2/3

“Quintessence” <~-0.8

“Phantom Energy” <-1

Reynald Pain


Ongoing high-z SN projects (SCP, HZT, HHZT) have o(200) SN Ia up to z=1.7 (about 20 above z=1). The projected statistical uncertainties will match estimated level of systematic uncertainties

=> Need 2nd generation experiments with both high statistics o(1000) and better control of possible systematics

Reynald Pain

snls the supernova legacy survey

SNLS – The SuperNova Legacy Survey


Reynald Pain

imaging survey with megacam at cfht
Imaging survey with Megacam at CFHT

CFHT :  3.6 m (1979)

Megacam (CEA/DAPNIA) : 1 deg2 , 4O CCD 2k*4K, = 328 Mpixel

First light : fall 2002

Reynald Pain

observation strategy rolling search
Observation strategy : “Rolling Search”

Part of the

CFHTLS/Deep survey

~ 40 nights/yr during 5 years

Repeated observations

(every 3-4n) of

4 sq. deg. in


Reynald Pain

cfht legacy survey deep

XMM deep








Groth strip



XMM deep

CFHT Legacy Survey/deep

Four 1 deg² fields (0226-04, 1000+02, 1419+53, 2215-18)

superb image quality (0.5-0.6 arc sec.)

queue scheduling, excellent temporal sampling

depth i’>24.5 (S/N=8, 1 hr); r’ > 28 in final stacked image

Reynald Pain

snls the spectroscopic survey
SNLS- The Spectroscopic survey

Goals :

- spectral id of SNe up to z~0.9

- redshift (host galaxy)

- detailled study of a subsample of SNe, Type IIs

(complementary programs, …)

Where? :

- VLT Large program (service) : 240h in 2003+2004

- Gemini : 60h/semester

- Keck : 3n/year (1st semester)

- Magellan : 2n/semester

Reynald Pain

find candidates how it works
Find candidates: How it works
  • Two independent search pipelines
  • PSF-match the “reference” and “new” images
  • Subtract…
  • … and search the difference images

PSFmatch errors from saturated objects easily rejected

Real candidate

Reynald Pain

current status typical light curves
Current status – typical light-curves

Typical time-sampling and light-curve coverage

Reynald Pain

june 2003 i 1 hr
June 2003 i’ 1 hr

z=0.281 SN Ia-p t=-7d

Reynald Pain

current status vlt spectroscopy
Current status – VLT spectroscopy





Reynald Pain


SNLS: Spectroscopy obs. June 03- Oct. 04

~160 SN Ia as of

Dec 04

Reynald Pain

snls progress
SNLS Progress

Reynald Pain

current status n z
Current status – N(z)

SNe from Sep 2003  Sep 2004

~115 SN Ia from a 12 month period

Distribution appears as expected out to z=0.9

Total predicted number of spectroscopically followed SNe

Reynald Pain

snls 1st year hubble diagram
SNLS : 1st year Hubble diagram

constraint on w (flat Universe)

72 SN at z = 0.2 - 0.95 + historical Calan-Tololo SNe

Reynald Pain

  • SNe Ia are excellent distance indicators
  • Ongoing SN experiments are reaching the systematic limit
  • 2nd generation projects are getting more and higher quality data. Toward building a Hubble diagram with ~1000 SN Ia
  • SNLS has collected ~160 SNIa in ~1.5 yr. 4 more years to go: expect many more SNe

Reynald Pain

precision cosmology with sn ia
Precision cosmology with SN Ia

Detect/follow SN Ia from Spacee.g. SNAPProposed 1999 Now running for NASA/DOE JDEM AO (2006?)

Reynald Pain

snap concept
SNAP concept

Observables :

Light Curves


Redshift & spectral properties

M and L

w and w’





Reynald Pain

snap strategy precision on w
SNAP: strategy - precision on w

Area : 2x7.5 sq. deg.

Cadence : 4 days

Total duration : 3 yr

60% imaging - 40% spectro

Total nb of SN : ~ 2000

contraints on w vs WM

(statistics + systematics)

+ 300 nearby SNe z>0.1

Reynald Pain

an alternative observing strayegy
An alternative observing strayegy

Basic concept

Many SNe - Precise space imaging

Ground based spectroscopy


100 sq deg. (UBVRIZ, I=26) + 10 sq. deg. (IZJHK, I=28)

Cadence: 4days (50% on deep survey)

Photométric id of SNe (UBV restframe)

Ground based spectroscopy (host galaxies)

=> 12000 SNe 0.1<z<2 in ~18 months

better statistical uncertainties on w, w’

calibration/systematic uncertainties ?

Reynald Pain

snap testing quintessence models
SNAP: testing quintessence models


0.08 w0=0.05

Reynald Pain

jdem destiny

Selected by NASA for « Einstein Probes 2yr Conceptual Studies »

f=1.8m telescop

0.25 deg. carrés - NIR 0.9->1.7 m

all grism R=100 (spectrophotometry)

L2 orbit


4 h exposure

7.5 sq. deg.

1.5 sq. deg./day (cadence 5 days)

2000 SNe 0.5<z<1.7 in 2 yrs

Calibration with ESSENCE/LSST (z<1)

Reynald Pain

dark universe explorer dune
Dark Universe Explorer (DUNE)

Proposed (2004) as weak lensing probe

1.2-1.5 m telescope

0.25-0.5 sq. deg. Imager

visible only - 1-2 filter

In phase O study at French Space Agency

If approved .. launch by 2011-12 ?

A SN program for DUNE ?

100 sq deg. (UBVRIZ, I=26) - cadence: 4days

Photométric id of SNe (UBV restframe)

Ground based spectroscopy (host galaxies)

=> 10000 SNe 0.1<z<1 in ~9 months

statistical uncertainties on w, w’ o(80%xSNAP)

calibration/systematic uncertainties ?

Reynald Pain