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= ) SNFactory (z= ) Prospects today (SN,Weak Lensing,BAO)

Cosmological parameters/expansion 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 (  = years) H(t) varies with time (Friedmann’s equations)

Cosmological parameters/expansion Friedmann’s equation (evolution of the Hubble ‘constant’) (From Einstein’s eq. with cosmological constant  density  i ) Deceleration: i :matter,radiation, cosmological constant p i = pressure Matter (p = 0) and radiation (p=  / 3) can only cause deceleration, while acceleration of the expansion is observed The 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 distance Some non standard interpretation of data still remain (inhomogeneities)

Supernovae flux The observed flux F from redshift is given by the luminosity distance d L (z): find d L (z) using a light ray: geometrical (propagation) distance  M =  M /  c,,      c  c = critical energy  time dilatation and Doppler reddening d L (z)=(1+z) R(z) z <<1 : d L (z) ~(1+z) z (recoil velocity proportional to distance~ H 0 z) Flux from SNIa probes directly  M,   (if constant!)

Supernova Ia thermonuclear explosion White dwarfs C + O core  ~ g/cm3, T = 106 K H and He layers blown away R ~ km 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: ergs, 1% optical L~ 10 9 L Spectral indications of unburnt Carbon seen (SNFACTORY) ‘onion’ structure C H ? O From accretion White dwarf + Companion

Standardisation Peak reached in ~ days Risetime~Diffusion Ni Co decay  =5.9 d Co Fe decay  =77.3d Initial mass close to M_chandra 1 main parameter: Ni mass produced Expect relations -luminosity/peak time -luminosity/colour(temperature) Stretch factor ~time scale standardises luminosity Colour correction improves further to ~10% intrinsic fluctuation SNIa can be used to probe cosmology (from SCP) Rest frame Blue Magnitude No correction stretch correction

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 SN Kernel kernel does NOT Exist mathematically (in general)

Spectral Identification Ca Fe S Si O Ca SNIa: Most absorption lines strongly Blended Lines are WIDE: velocity spread from explosion No Hydrogen lines: blown out before Strong Ca absorption lines Strong and characteristic Si line Identification from light curve alone may be possible (?). Spectrum at maximal luminosity Most spectra very similar 2 random SN shown NO 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/stretchMagnitude/colour colour/stretch uncorrelated Brighter-slower (Diffusion time) Brighter-Bluer (Higher temperature) Refined spectral correlations under investigation (Promising)

Equiv. Width correction Spectra,mostly intrinsic Colour correction combines blindly intrinsic + extinction Hubble Diagramm (SNLS) Observed luminosity redshift 1/r 2 law If 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 = w 0 + w 1 z Adjust w 0,w 1 to data (assuming a flat universe) Cosmological parameters -II ( w   w  ) As errors too large assume w1=0 Compatible with w = - 1 (cosmological Cste) Large errors Better experimental data needed Inhomogeneities 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 15x15 Galaxy + SN 6x6 arcs Dichroic 2 channel spectroscopy , 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 2004 Smooth 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 SNIa 166 SNe Ia > 5 spectra 2433 Spectra (~15/ SN) 142 SNIa >10 spectra AGN 25 Other 32 Asteroids 5 SNII 181 SNIa 406 SNIb/c(=SNII) 41 SN? 96 Unknown 42 Var 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 epochs 55 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 weather At Palomar(search)+ Fast selection + good weather at Hawaii

A Few Light curves

Hubble Diagram (clean SN,SNfactory) Available new observed (clean) 150 available Nearby Hubble Diagram New SNFACTORY Only Clean SNIA Analysed today: Galaxy subtraction In progress

Galaxy Subtraction /deconvolution (in progress) B Channel 10 wavelength metaslices Galaxy subtracted SN + Galaxy

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) kx2k 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 Systematic errors Determination of w 1 very hard even with SNAP Control of systematics needed to within 1% up to z = 1.7 Offset dispersion 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 (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 Typical gravitational ellipticity ~a few Averageing over millions of Galaxies needed Deflection angle  Lensing by mass (Newtonianx2)

Lensing by mass distribution D LS DLDL DSDS Lens: Deviation is proportional to mass SURFACE density :integral of Newton potential Moments characterize ellipticity

Weak Lensing Basics Lensing by 3D matter equivalent to sum of plane lenses with (projected) mass density   D prop 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, P  0 :primordial Cosmology enters in Fluctuations of  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 ) Need to control optical PSF to (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-spectroscopyStage 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 s s s s s Burnt fraction S f /xmax 2 = 43 S f /xmax 2 = 0.53 V 10 3 km/s V km/s V 10 3 km/s       S f = flame surface xmax = 5x10 8 cm Gamezo et al. (2002)simulation 3D A lot of simulation Effort…

Figure of Merit of different projects