Transcript Document

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
Describe uniform homogeneous (still debated) universe by
Robertson-Walker metric (only solution for Cste curvature)
ds2  a(t ) 2 R02 [r 2 (d 2  sin 2  (d ) 2 ) 
(dr ) 2
1  kr
2
]
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 :
z   
a( z)  1 (1  z)
(Doppler)
Hubble ‘constant’ = H0 = expansion rate  a (t  0) a(t  0)
~73km/s/Mpc (today)
H0 is the inverse of a time t: c t = distance at which
the expansion reaches the light velocity (t= 12.5 109 years)
H(t) varies with time (Friedmann’s equations)
Cosmological parameters/expansion
Friedmann’s equation (evolution of the Hubble ‘constant’)
2
a a  8G 3   i   3  k a
(k  0)
(From Einstein’s eq. with cosmological constant , density i)
Deceleration:
3 pi
a a   4G 3 (  i  2 )   4G 3 (  M a 3     3  )
c
i :matter ,radiation, cosmological constant pi = 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
z   
The observed flux F from redshift
is given by the luminosity distance dL(z):
F  ( L 4d L ( z)2 )
find dL(z) using a light ray:
a(t )dr  cdt
r ( z )   cdt a  c
a ( z ) 1 /(1 z )
2
da
(
a
(a / a ))

a ( 0 ) 1
geometrical (propagation) distance
R( z )  c H 0  da (a 2 (W M a 3  W  ))
WM = M/c , , W  /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 WM , W (if constant!)
Supernova Ia thermonuclear explosion
‘onion’ structure
White dwarf + Companion
White dwarfs
C + O core
From
accretion
 ~ 5 109 g/cm3, T = 106 K
H and He layers
O
blown away
R ~ 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)
H?
C
Standardisation
(from SCP)
No
correction
Peak reached in ~ 15-20 days
Risetime~Diffusion
Ni
Co decay t =5.9 d
Co
Fe decay t =77.3d
Initial mass close to M_chandra
1 main parameter: Ni mass produced
Expect relations
-luminosity/peak time
-luminosity/colour(temperature)
stretch
correction
Rest frame Blue Magnitude
Stretch factor ~time scale
standardises luminosity
Colour correction improves further
to ~10% intrinsic fluctuation
SNIa can be used to probe
cosmology
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
Galaxy + SN
Reference image
Convoluted reference /kernel
Galaxy, good seeing degrade ref to observed seeing
kernel does NOT
Exist mathematically
(in general)
Profile of galaxy
Images
Kernel
Subtracted image
with SN
Spectral Identification
Spectrum at maximal luminosity
Most spectra very similar
2 random SN shown
NO quantitative model/understanding of explosion yet
(Model + radiative transfer)
SNIa:
Most absorption lines strongly
Blended
Lines are WIDE: velocity spread
from explosion
Ca
Fe
No Hydrogen lines: blown out
before
Strong Ca absorption lines
Strong and characteristic Si line
Fe
Si
S
O
Ca
Identification from light curve
alone may be possible (?).
Stretch and colour
Magnitude/stretch
(from SNLS-1st year)
Magnitude/colour
(from SNLS-1st year)
Colour/stretch (SNFACTORY)
Magnitude/stretch
Magnitude/colour
•Brighter-slower
(Diffusion time)
•Brighter-Bluer
(Higher temperature)
colour/stretch •Refined spectral
uncorrelated
correlations under
investigation
(Promising)
Hubble Diagramm (SNLS)
Equiv. Width correction
Spectra,mostly intrinsic
Colour correction
combines blindly intrinsic + extinction
1/r2 law
If H(z)=H0
Observed
luminosity
About 15%
Spread, 10%
intrinsic
redshift
Cosmological parameters-1 (WM,W)
Cosmological parameters -II (w0,w1)
• 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)
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.
Filter wheel
Tel
Dichroic
Microlens
Arrays
15x15
Galaxy + SN
6x6 arcs
•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)
SNIa thermonuclear
SNII gravitational collapse
H lines
No Si
SNIb,c = SNII
no H (blown)
+ some Si
First light SNIFS 2004
Smooth data taking spring 2005
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
Other
Asteroids
SNII
SNIa
SNIb/c(=SNII)
SN?
Unknown
Var stars
25
32
5
181
406
41
96
42
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
256
Nearby Hubble Diagram
New SNFACTORY
51
Only Clean SNIA
Analysed today: Galaxy subtraction
In progress
40 new observed (clean)
150 available
Galaxy Subtraction /deconvolution (in progres
SN + Galaxy
B Channel
Galaxy subtracted
10 wavelength metaslices
Subtracted SN spectrum
1.2
SNF20051003-004
x1e-15
spec_CE3Dfullsub_05_281_064_B169.fits (T=1000s, z=1.01)
spec_CE3Dfullsub_05_281_064_R169.fits (T=1000s, z=1.01)
1.0
Flux [FLAM]
0.8
0.6
0.4
0.2
0.0
0.3
0.4
0.5
0.6
0.7
Lambda [A]
0.8
0.9
1.0
x1e+4
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)
• USA:
Weak Lensing, Baryon Acoustic Oscillation,Galaxy distribution
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 (WM,W)
(From ground to space)
Supernovae 1% systematics
SNAP + SNFACTORY 300 Nearby + 2000
Systematic errors
Kim et al. (2003)
Offset
dispersion
slope
Filter offset systematics
Filter correlated shift
•Determination of w1 very hard even with SNAP
Control of systematics needed to within 1% up to z = 1.7
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
Lensing by mass
Deflection angle a
4GM
a
bc 2
(Newtonianx2)
dDprop  cdt
Typical gravitational ellipticity
~a few 10-3
Averageing over millions of
Galaxies needed
Lensing by mass distribution
Moments characterize e  I xx  I yy

I xx  I yy
ellipticity
Lens:
e 
I xx  I yy
I xx  I yy
DLS
e 
DL
I xx  I yy

I xx  I yy
1
2
  arctg(
e
)
e

  DLS
    a ( )
DS
Deviation is proportional
 to mass
SURFACE density ( )
DS
I xx  I yy
e 
2I xy
 
1 
a ( )  2 
c
:integral of Newton potential


( )  8G( )

DLS
( )  2
dz

DL DS

Weak Lensing Basics
• Lensing by 3D matter equivalent to sum of plane
lenses with (projected) mass density 
4G DL DLS dDprop
k 2
d
c
DS
dz
0
zn
dDprop  cdt
Cosmology enters in
Fluctuations of d
Dprop is propagation time
k 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
Cosmology enters in
Pd  D ( z)T 2 (k )Pd0 (k )
2
D+(z), astrophysics in T(k)
• D: Growth factor,T:transfer, Pd0:primordial
Weak Lensing next generation
Stage IV-LSST
Wide Physics field for
LSST (10m,2015?)
SKA (Radio,2020?)
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 III-photometry
Stage III-spectroscopy
Stage IV-LSST
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
V 103 km/s
A lot of simulation
Effort…
12
2
3D
1.487 s
V 103 km/s
0.3950
Burnt fraction
Sf/xmax2 = 0.53
Gamezo et al.
(2002)simulation
1.760 s
0.4650
0.2663
12
2
1.573 s
V 103 km/s
1.652 s
0.1002
V km/s
1.257 s
12
2
0.3344
1.902 s
0.5255
Sf = flame surface
xmax = 5x108cm
Sf/xmax2 = 43
Figure of Merit of different projects