Paris - Apr29, 2005Reynald Pain 1998-2003 : Concordance model Today’s question : Cosmological Constant, Vacuum Energy or Dark Energy ? SNe Ia prefer

Paris - Apr29, 2005 Reynald Pain

1998-2003 : Concordance model

Today’s question :

Cosmological Constant, Vacuum Energy

or Dark Energy ?

SNe Ia prefer

a non zero


Outline:

• Cosmology with SNe Ia

• Why keep studying SNe Ia ?

• SNLS - the SuperNova Legacy Survey


Cosmology with SNe Ia

Luminosity distance : dL(z)

SNe Ia ?


SNe Ia are not standard candles

Very Luminous events visible at cosmological

distances

Show little intrinsicdispersion


SNe Ia Show Light Curve Shape Relationships

(similar to Cepheids P-L relation)

=> Allows to measure distances to better than

5-8% precision

Measuring distances


From fainter to brighter…

SN Ia Spectral features


Models ObservationsUsing 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.

SNe Ia modelisation


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 ?


HST measured color

SCP 2003

+11 SN photometrically followed with HST allows event by event extinction correction

Updated Hubble diagramUsing a low extinction subset


“Morphological” Hubble diagram

SCP 2002

Is there a host galaxy effect ?


SNe at higher redshift (Goods/ACS survey)

Probe the deceleration era

Find Sne at z>1.2 using HST


GOODS/ACS 2004: HST Supernovae

Expansion went from deceleration to acceleration

Exclude grey dust


Probe Dark Energy

Source w

Matter 0Radiation 1/3Cosmo Cte -1Scalar field (cte) -1 Cosmic strings -1/3Domain wall -2/3“Quintessence” <~-0.8“Phantom Energy” <-1

Other sources : w = p/Cosmological constant : p=-


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


SNLS – The SuperNova Legacy Survey

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


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


Observation strategy : “Rolling Search”

Part of the CFHTLS/Deep survey

~ 40 nights/yr during 5 years

Repeated observations (every 3-4n) of4 sq. deg. in

ugriz


CFHT Legacy Survey/deep

XMM deepVIMOSSWIREGALEX

Cosmos/ACSVIMOSSIRTFXMM …

Groth stripDeep2ACS …

XMM deep

Four 1 degFour 1 deg² ² fields (0226-04, 1000+02, 1419+53, 2215-18)fields (0226-04, 1000+02, 1419+53, 2215-18)

superb image quality (0.5-0.6 arc sec.)superb image quality (0.5-0.6 arc sec.)queue scheduling, excellent temporal samplingqueue scheduling, excellent temporal samplingdepth i’>24.5 (S/N=8, 1 hr); r’ > 28 in final stacked imagedepth 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


SNLS- The Spectroscopic surveyGoals : - 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


Find candidates: How it works

• Two independent search pipelines• PSF-match the “reference” and “new” images• Subtract…• … and search the difference images

Real candidate

PSFmatch errors from saturated

objects easily rejected


Search/follow-up of SNe


Current status – typical light-curves

Typical time-sampling and light-curve coverage


June 2003 i’ 1 hr

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


Current status – VLT spectroscopy

z=0.550 z=0.610

z=0.815 z=0.988


SNLS: Spectroscopy obs. June 03- Oct. 04

~160 SN Ia as of

Dec 04


SNLS Progress


Current status – N(z)

Total predicted number of spectroscopically followed SNe

Distribution appears as expected

out to z=0.9

~115 SN Ia from a 12

month period

SNe from Sep 2003 Sep 2004


SNLS : 1st year Hubble diagram

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

constraint on w (flat Universe)


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



Precision cosmology with SN Ia

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


Images

Spectra

Redshift & spectral properties

Light Curves

data analysis physics

M and

w and w’

SNAP concept

Observables :


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 vsM

(statistics + systematics)

+ 300 nearby SNe z>0.1


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 ?


SNAP: testing quintessence models

w´=0.08

w0=0.05


JDEM/DESTINYSelected by NASA for « Einstein Probes

2yr Conceptual Studies » =1.8m telescop 0.25 deg. carrés - NIR 0.9->1.7 all grism R=100 (spectrophotometry) L2 orbitSurvey: 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)


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 ?

Documents

Paris - Apr29, 2005Reynald Pain 1998-2003 : Concordance model Today’s question : Cosmological Constant, Vacuum Energy or Dark Energy ? SNe Ia prefer