Supernovae Measurements in Cosmology

G. Smadja, Institute of Nuclear Physics of Lyon(IPNL) Cl. Bernard University

Outline

• Context: Cosmological parameters and expansion

• Supernovae: Progenitor,Light curve,standardisation

• Observations: SNLS like surveys (CFHT,Photometry)

• SNLS results (z=0.1-0.9)

• SNFactory (z=0.03-0.1)

• Prospects today (SN,Weak Lensing,BAO)

Cosmological parameters/expansion

]1

)())(sin([)(

2

222222

022

kr

drddrRtads

)0()0( tata

Describe uniform homogeneous (still debated) universe by Robertson-Walker metric (only solution for Cste curvature)

k = 0 for flat universe, assumed in following (±1 curved space ) a(t) is the scale factor of the expansion a(t=0) = 1 (today)

At redshift z : (Doppler) Hubble ‘constant’ = H0 = expansion rate ~73km/s/Mpc (today)H0 is the inverse of a time : c = distance at which the expansion reaches the light velocity (= 12.5 109 years)H(t) varies with time (Friedmann’s equations)

z )1(1)( zza

Cosmological parameters/expansion

)3(34)3

(34 32

aGc

pGaa M

ii

2338 akGaa i

Friedmann’s equation (evolution of the Hubble ‘constant’)

(From Einstein’s eq. with cosmological constant

density i)

Deceleration:

i :matter ,radiation, cosmological constant pi =

pressureMatter (p = 0) and radiation (p= / 3) can only cause deceleration, while acceleration of the expansion is observedThe positive contribution from the cosmological constant(p = -) is needed to account for the accelerated expansion adds a (small) repulsive contribution to newtonian gravitation, proportional to distanceSome non standard interpretation of data still remain (inhomogeneities)

)0( k

Supernovae flux The observed flux F from redshift is given by the luminosity distance dL(z):

find dL(z) using a light ray: geometrical (propagation) distance

M = M/c , , c c = critical energy time dilatation and Doppler reddening dL(z)=(1+z) R(z) z <<1 : dL(z) ~(1+z) z

(recoil velocity proportional to distance~ H0 z)

Flux from SNIa probes directly M , (if constant!)

z))(4( 2zdLF L

cdtdrta )(

))/(()()1/(1)(

1)0(

2 aaadacacdtzrzza

a

))(()( 320

aadaHczR M

Supernova Ia thermonuclear explosion

White dwarfs C + O core~ 5 109 g/cm3, T = 106 KH and He layersblown awayR ~ 2000-10000km M< 1.4 M (Chandrasekhar) •White dwarf accreting from companion

(1/1000year/galaxy)•Thermonuclear fusion explosion triggered as M 1.4 M And R 0 •Initial phase of explosion and power NOT well understood•Total Power released: 10 51 ergs, 1% optical L~ 109 L •Spectral indications of unburnt Carbon seen (SNFACTORY)

‘onion’ structure

CH ?

O

From accretion

White dwarf + Companion

Standardisation Peak reached in ~ 15-20 daysRisetime~Diffusion Ni Co decay =5.9 dCo Fe decay =77.3dInitial mass close to M_chandra1 main parameter: Ni mass produced

Expect relations-luminosity/peak time-luminosity/colour(temperature)

Stretch factor ~time scale standardises luminosityColour correction improves further to ~10% intrinsic fluctuation SNIa can be used to probe cosmology

(from SCP)

Rest frame Blue Magnitude

Nocorrection

stretchcorrection

Experimental Method

• SNLS = 36 2kx2k CCD at Canadian French Hawaii Telescope,

(4m diameter)• Take ‘reference’ images of star field date 1• Detect variable sources by subtraction date2-date 1• Select SNIa candidates (about ~300 true /year/20 deg

z<0.9) (Use time dependence of luminosity, colour, neighbourhood of galaxy,

etc…) • Take a spectrum of all or of a subsample of candidates to confirm typing of SNIa

• Difficulties:• Atmosphere : ‘seeing’ (spot of point source) changes, naive subtraction does not work: degrade reference to observation day with convolution kernel

• variable sources: asteroids, satellites,AGN,cepheids, etc…

eliminate with light curve, spectrum, colour

Subtraction in SNLS Observation Reference image Convoluted reference /kernel Galaxy + SN Galaxy, good seeing degrade ref to observed seeing

Images

Profile of galaxy

Subtracted image with SNKernel

kernel does NOT Exist mathematically(in general)

Spectral Identification

Ca

Fe

Fe

S

Si

O Ca

SNIa:Most absorption lines stronglyBlendedLines are WIDE: velocity spread from explosion No Hydrogen lines: blown out beforeStrong Ca absorption linesStrong and characteristic Si line

Identification from light curvealone may be possible (?).

Spectrum at maximal luminosity Most spectra very similar 2 random SN shownNO quantitative model/understanding of explosion yet(Model + radiative transfer)

Stretch and colour

Magnitude/stretch(from SNLS-1st year)

Magnitude/colour(from SNLS-1st year)

Colour/stretch (SNFACTORY)

Magnitude/stretch Magnitude/colour

colour/stretchuncorrelated

•Brighter-slower(Diffusion time)

•Brighter-Bluer(Higher temperature)

•Refined spectral correlations under investigation (Promising)

Equiv. Width correctionSpectra,mostly intrinsic

Colour correctioncombines blindly intrinsic + extinction

Hubble Diagramm (SNLS)

Observed luminosity

redshift

1/r2 lawIf H(z)=H0

About 15% Spread, 10%intrinsic

Cosmological parameters-1 ()

• Why (close to but not equal to 0 whatever it means) ?

• Extend to (time dependent) classical field (quintessence)

• Equation of state of ‘field’ p = w(z) (from stress tensor)

w = -1 for a cosmological constant• Parametrize w = w0 + w1z

• Adjust w0,w1 to data (assuming a flat universe)

Cosmological parameters -II (ww)

As errors too large assume w1=0Compatible with w = -1 (cosmological Cste)Large errorsBetter experimental data neededInhomogeneities unlikely

Improving data on Eq. of state

•Dark energy constant or field? Constant simpler, field has strange features, but …

•Data must be improved •Decrease systematics (10%) (Go to space)•Extend range/lever arm

•Up to z=1.7 (Go to space + NIR detectors)•Down to 0.03<z<0.1 (more statistics)

•Use other techniques:Weak Lensing, BAO

•SNFactory adresses the low z issue•Spectrophotometry as a tool for

•Understanding of SN explosions•Tests of evolution from near (low z) to distant (high z) •Create spectral templates at all phases for light curves

The SNFACTORY collaboration

•Cover the range 0.03<z<0.1 (Hubble flow + exposure time)•Measure spectra at all dates : improve light curve measurements In photometric filters (time dependent create templates)•Measure the total flux: no slit spectroscopy Integral Field Spectrograph

•SNFACTORY Collaboration: LBNL (Berkeley)Aldering,Perlmutter Yale C. Baltay CRAL(Lyon) Pecontal IPNL(Lyon) G. S.,Y.Copin LPNHE(Paris) R. Pain

•Search at Quest 1m,Palomar, Yale CCD Camera (US teams)•Spectroscopy at UH 2m with IFS SNIFS from Lyon

The SNIFS Integral field Spectrograph

Cal.

Tel

Filter wheel

Microlens Arrays 15x15Galaxy + SN6x6 arcs

Dichroic

•2 channel spectroscopy 320-520, 510-1000 nm

•Photometry 9.5’x9.5’ field of view acquisition of images guiding Extinction monitoring•Internal Calibration Arc Lamps + Continuum

•0.43x0.43 arcs/microlens

Search in SNFACTORY (July 2008)

First light SNIFS 2004Smooth data taking spring 2005

SNIa thermonuclear

SNII gravitational collapse H lines No Si

SNIb,c = SNII no H (blown) + some Si

SNFACTORY Sample (July 2008)

Update Sept 2008

Spectra by SNIFS 901 targets

3545 spectra

SNIa166 SNe Ia > 5 spectra2433 Spectra (~15/ SN)142 SNIa >10 spectra

AGN 25Other 32Asteroids 5SNII 181SNIa 406SNIb/c(=SNII) 41SN? 96Unknown 42Var stars 73

A typical SN spectral spectrum

•Fe dominates the general trends•Lines are blended (many atomic levels)•NO Black-Body like Continuum

A Time sequence

17 epochs55 days

Flux measurement

Photometric (stable) nights: use calibration by known reference star

Non Photometric night: use photometric channel compare star fields with same in photo night

Main difficulty for flux estimate in spectro channel: good description of response to point source is needed (PSF,mostly atmospheric). changes from expo to expo (turbulence)

Other difficulty for SNIa: subtract host galaxy. Reference image needed, but PSF different only 1 star, no Kernel constraints.

Standard star light curve (synthetic filters)

• Test Case GD71 (V = 13) • 31 expo. various atm. conditions• ~3% flux accuracy 350 to 920 nm

2%

Supernovae light curves (synt. Filters/clean SN)

Sometimes good atmospheric conditions over 60 days Early data usually hard to obtain at small z: good weatherAt Palomar(search)+ Fast selection + good weather at Hawaii

A Few Light curves

Hubble Diagram (clean SN,SNfactory)

Available

51

256

40 new observed (clean)150 available

Nearby Hubble DiagramNew SNFACTORY

Only Clean SNIAAnalysed today: Galaxy subtractionIn progress

Galaxy Subtraction /deconvolution (in progress)

B Channel

10 wavelength metaslices

Galaxy subtracted SN + Galaxy

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0Lambda [A] x1e+4

0.0

0.2

0.4

0.6

0.8

1.0

1.2Fl

ux [F

LAM

]

x1e-15 SNF20051003-004

spec_CE3Dfullsub_05_281_064_B169.fits (T=1000s, z=1.01)spec_CE3Dfullsub_05_281_064_R169.fits (T=1000s, z=1.01)

Subtracted SN spectrum

Peculiar SNIa

Super Chandrasekar SNIa 2 WD?

Future SN projects: Space

• Projects in Europe and USA on Dark Energy

• Europe: ESA Cosmic vision (DUNE/Space= EUCLID) Weak Lensing, Baryon Acoustic Oscillation,Galaxy

distribution• USA: Beyond Einstein (Adept,Destiny,SNAP) Adept:Near IR/grisms: BAO + SNIa Destiny:Near IR/grisms 0.5<z<1.7,SNIa+SNII (grism = slitless spectro with grating on small prism) JDEM Supernovae: imager (+ spectro) visible (CCD) + IR(pixels) 36 +36 2kx2k Weak Lensing,(BAO) •Proposals due in Fall•Selection decision next spring

Science Goals SNAP/SN () (From ground to space)

Supernovae 1% systematics

SNAP + SNFACTORY 300 Nearby + 2000 Systematic errors

•Determination of w1 very hard even with SNAP

Control of systematics needed to within 1% up to z = 1.7

Offsetdispersion

slope

Kim et al. (2003)

Filter offset systematics Filter correlated shift

Control of systematic errors in SNAP

•Challenging

•Filters must be controlled to a few 10-3

(despite ageing/cosmic rays + solar eruptions) •Good monitoring of pointing and PSF (Flux)

•Detailed monitoring of detector behaviour(Temperature stability, non linearity, Persistence, response maps, interpixel Properties, intrapixelproperties, etc…)

•Cross-check by other methods desirable

Cosmology with Weak Lensing

Lensing by mass

cdtdDprop

Typical gravitational ellipticity

~a few 10-3

Averageing over millions of Galaxies needed

Deflection angle

2

4

bc

GM

Lensing by mass

(Newtonianx2)

Lensing by mass distribution

yyxx

yyxx

II

IIe

S

LS

D

D)(

yyxx

yyxx

II

IIe

)(2

1

e

earctg

yyxx

yyxx

II

IIe

DL

S

DL

DS

Lens:

Deviation is proportional to mass SURFACE density

:integral of Newton potential

yyxx

xy

II

Ie

2

)(

2

1)(c

)(8)(

G

dzDD

D

SL

LS2)(

Moments characterize ellipticity

Weak Lensing Basics

• Lensing by 3D matter equivalent to sum of plane lenses with (projected) mass density

Dprop is propagation time characterises the convergence of the lens• ‘Cosmic shear’ measures mass distributions at

lower redshift than CMB• Maps dark matter• Probes dark energy at low redshifts

(subdominant at high redshifts

• D: Growth factor,T:transfer, P0:primordial

dz

dD

D

DD

c

G prop

S

LSL

zn

0

2

4

cdtdDprop

Cosmology enters in Fluctuations of

)()()( 022 kPkTzDP Cosmology enters in D+(z), astrophysics in T(k)

Weak Lensing next generation

Wide Physics field for LSST (10m,2015?) SKA (Radio,2020?)

Stage IV-LSST Stage IV-SKA

Determination of w (space/SNAP)

(Equation of state) Potential of weak lensing

Weak lensing systematics

• Mainsystematic is linked to instrumental/atmospheric PSF• Telescope distorsions generate ‘fake’ distorsion

correlations, must be corrected

• Effect is much larger than gravitational lensing (a few 10-

3)

• Need to control optical PSF to 10-7 (including pointing) For w measurement

• ‘at the edge’

Baryon Acoustic Oscillation

Similar to CMB, replace radiation by galaxies

Baryonic Acoustic Oscillation Stage IV-LSST Stage III-photometry

Stage III-spectroscopy Stage IV-SKA

Conclusions• SNIa is now a ‘mature’ probe, although not fully understood. • Space experiments needed for progress on cosmology/SN• Even in space,constraining dark energy with SNIa will be difficult• Other techniques: BAO promising, lots of room for improvements, not very sensitive to • Weak lensing: powerful, tough systematics/PSF• CMB: not really sensitive to • Universe is a ‘relevant’ laboratory

Back Up

1.257 s

1.487 s

1.573 s

1.652 s

1.760 s

1.902 s

0.3950

0.4650

0.52550.3344

0.2663

0.1002

Burnt fraction

Sf/xmax2 = 43

Sf/xmax2 = 0.53V 1

03 km

/s

V k

m/s

V 1

03 km

/sV

103 k

m/s

Sf = flame surface

xmax = 5x108cm

Gamezo et al.(2002)simulation

3D

A lot of simulation Effort…

Figure of Merit of different projects