1998-2003 : Concordance model
SNe Ia prefer
a non zero L
Today’s question :
Cosmological Constant,
Vacuum Energy
or
Dark Energy ?
Paris - Apr29, 2005
Reynald Pain
Outline:
• Cosmology with SNe Ia
• Why keep studying SNe Ia ?
• SNLS - the SuperNova Legacy Survey
Paris - Apr29, 2005
Reynald Pain
Cosmology with SNe Ia
Luminosity distance : dL(z)
SNe Ia ?
Paris - Apr29, 2005
Reynald Pain
SNe Ia are not standard candles
Very Luminous events
 visible at cosmological
distances
Show little intrinsic
dispersion
Paris - Apr29, 2005
Reynald Pain
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
Paris - Apr29, 2005
Reynald Pain
SN Ia Spectral features
From fainter to brighter…
Paris - Apr29, 2005
Reynald Pain
SNe Ia modelisation
Models
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.
Paris - Apr29, 2005
Reynald Pain
Observations
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 ?
Paris - Apr29, 2005
Reynald Pain
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
Paris - Apr29, 2005
Reynald Pain
“Morphological” Hubble diagram
SCP 2002
Is there a host galaxy
effect ?
Paris - Apr29, 2005
Reynald Pain
SNe at higher redshift (Goods/ACS survey)
Probe the
deceleration era
Find Sne at
z>1.2 using HST
Paris - Apr29, 2005
Reynald Pain
GOODS/ACS 2004: HST Supernovae
Expansion went from
deceleration to
acceleration
Exclude grey dust
Paris - Apr29, 2005
Reynald Pain
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
Paris - Apr29, 2005
Reynald Pain
But:
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
Paris - Apr29, 2005
Reynald Pain
SNLS – The SuperNova Legacy Survey
http://cfht.hawaii.edu/SNLS/
Paris - Apr29, 2005
Reynald Pain
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
Paris - Apr29, 2005
Reynald Pain
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
ugriz
Paris - Apr29, 2005
Reynald Pain
CFHT Legacy Survey/deep
Four 1 deg² fields (0226-04, 1000+02, 1419+53, 2215-18)
XMM deep
VIMOS
SWIRE
GALEX
Cosmos/ACS
VIMOS
SIRTF
XMM …
Groth strip
Deep2
ACS …
XMM deep
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
Redshift
0.3 0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
Total
Ia
7
8
11
13
14
15
15
16
16
16
131
Ib/c + II
12
16
20
16
12
—
—
—
—
—
76
Expected nb of SN per semester
Paris - Apr29, 2005
Reynald Pain
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
Paris - Apr29, 2005
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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
Paris - Apr29, 2005
Real candidate
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Search/follow-up of SNe
Paris - Apr29, 2005
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Current status – typical light-curves
Typical time-sampling and light-curve coverage
Paris - Apr29, 2005
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June 2003 i’ 1 hr
z=0.281 SN Ia-p t=-7d
Paris - Apr29, 2005
Reynald Pain
Current status – VLT spectroscopy
z=0.550
z=0.610
z=0.815
Paris - Apr29, 2005
Reynald Pain
z=0.988
SNLS: Spectroscopy obs. June 03- Oct. 04
~160 SN Ia
as of
Dec 04
Paris - Apr29, 2005
Reynald Pain
SNLS Progress
Paris - Apr29, 2005
Reynald Pain
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
Paris - Apr29, 2005
Reynald Pain
SNLS : 1st year Hubble diagram
72 SN at z = 0.2 - 0.95 + historical Calan-Tololo SNe
constraint on w
(flat Universe)
Paris - Apr29, 2005
Reynald Pain
Summary
• 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
Paris - Apr29, 2005
Reynald Pain
Paris - Apr29, 2005
Reynald Pain
Precision cosmology with SN Ia
Detect/follow
SN Ia from Space
e.g. SNAP
Proposed 1999
Now running for NASA/DOE
JDEM AO (2006?)
Paris - Apr29, 2005
Reynald Pain
SNAP concept
Observables :
Light Curves
Images
Redshift & spectral properties
M and L
w and w’
Spectra
data
Paris - Apr29, 2005
Reynald Pain
analysis
physics
SNAP: strategy - precision on w
Area : 2x7.5 sq. deg.
contraints on w vs M
Cadence : 4 days
(statistics + systematics)
Total duration : 3 yr
60% imaging - 40% spectro
Total nb of SN : ~ 2000
+ 300 nearby SNe z>0.1
Paris - Apr29, 2005
Reynald Pain
An alternative observing strayegy
Basic concept
Many SNe - Precise space imaging
Ground based spectroscopy
Survey:
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 ?
Paris - Apr29, 2005
Reynald Pain
SNAP: testing quintessence models
w´=
0.08
w0=0
.05
Paris - Apr29, 2005
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
Survey:
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)
Paris - Apr29, 2005
Reynald Pain
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 ?
Paris - Apr29, 2005
Reynald Pain