Transcript Padova talk

Six years of Dark Energy: present and
future prospects
Ariel Goobar
Physics Department, Stockholm University
SCP:Perlmutter et al + High-Z Team:Riess et al
Supernova
Cosmology
Project (SCP)
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Year 5 AD
Sullivan et al 2003
Redshift
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5 AD: concordance model
(see also Tonry et al 2003, Barris et al 2004)
SS
IS
Independent evidence
also from eg:
LSS (eg Peacock et al)
ISW (eg Boughn & Crittenden)
Cluster abundances (eg
Bahcall et al)
Age of Universe
X-ray clusters (Allen et al 04)
0.06
   0.75 0.07  0.04
stat syst
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SN1a: systematic effects
No
extinction
correction.
Reddened
SNe
excluded
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With
extinction
correction
Non-Type Ia contamination
Malmquist bias
K-corrections and SN colors
Extinction by host galaxy dust
Extinction by intergalactic dust
SN brightness evolution
Shape-brightness relation
Instrumental corrections
Lightcurve fitting technique/host
galaxy subtraction
Gravitational lensing
Exotica: axion-photon oscillations, etc
…
Largest source of
identified syst in
Knop et al:
uncertainty in the
intrinsic colors of
SN1a ar short l
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Spectroscopic tests of standard candle
subluminous
overluminous
CaII (3900)
velocity
subluminous
Folatelli et al, Garavini et al , Lidman et al
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Statistical uncertainty:
Redshift dependence
AG & Perlmutter 95 95
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Turning 6! Very-high Z supernovae from
ACS/HST (Riess et al 2004)
•>19 SNe discovered
from space, up to z=1.7
•Reported CL-regions
due to statistical errors
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Extinction corrections
Riess et al 2004 (gold sample)
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Uncertainties ?
z-dependence in reported Av ?
Problems with K-corrections/assumed
intrinsic colors in UV part of the SNIa
spectrum?
Changing dust properties ?
Selection effects?
Watch out for priors on AV! Riess et al
assume P(Av)~exp(-Av)
A careful study of extinction
correction systematics for z>0.9 SNe
(as done in Knop et al for z<0.9) is still
missing.
SN97ff:
assumed
extinctionfree, E-host
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Gray(er) IG dust
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Large dust grains (weak wavelength
dependence) may populate the IGmedium (Aguirre 1999,2000)
• Evolution of dust density: two limiting
cases considered:
1. dust (1+z)3 [Model A]
2. dust (1+z)3 for z<0.5 &
dust(z>0.5)= dust(z=0.5) [Model B,
”replenishing dust”]
• Hard to rule out from SN-colors
• X-ray point-sources at very high-z,
(e.g. Paerels et al) do not exclude e.g
Model B
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AG,Bergström & Mörtsell, A&A, 2002
Model A
Concordance
Milne
ModelB;
M=1
SDSS QSO colors (2740 objects, z<2)
Dust
still
a serious
concern
for
<0.2ismag
extinction
for SN1a
at z=1;
faintnesscosmology
of SNe unlikely
to only
precision
withdue
SNe.
IG-dust
Mörtsell & AG, JCAP, 2003
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Download: www.physto.se/~ariel
MC + cosmology fitting code specifically
developed to understand science reach and
systematic uncertainties in observations of
high-z SNe, e.g. due to intervening dust
gravitational lensing, search biases, non-SNIa
contamination, etc.
A.G et al (2002) Astronomy & Astrophysics, 392,757
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bias in the cosmology fit
due to lensing
20% co
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GL →asymmetric mag. distributions
Bias in cosmological results
However, with proper statistical
treatment bias can be kept low +
fraction of compact objects in DM
derived
Mörtsell, Gunnarson, AG, ApJ, 2001; SNAP simulations, Mörtsell, AG, Bergström.
ApJ, 2001; Amanullah, Mörtsell, AG; A&A, 2003
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Is Dark Energy =  ?
Although  appears to be the ”simplest”
explanation to the data, there are fundamental
theoretical problems:
1) why so small?
2) why is the vacuum density so close to matter
density now?
present SN data consistent with with w=-1, i.e
cosmological constant, although rapid evolution
has been suggested...
Tobias Goobar, age 6
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Rapidly changing w?
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Seems like reasonable parametrization,
however...
•The expression of w comes from
derivatives of ansatz in H(z)
•Parts of parameter-space causes
divergences
•As z increases, limiting value of wDE≠-1
•Parametrization ”forces” Metamorphosis
Alam et al (2003,2004) proposed fitting
SN data with truncated Taylor
expansion for DE.
Claim: signs for rapid evolution in w:
Metamorphosis
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Theoretical systematics
Test: simulate + fit 500 experiments , z-distribution and
uncertainties as in Tonry + Barris et al
cosmology
Metamorphosis
not required to
explain the fits!
”Transition
redshift” set by
Jönsson, AG, Amanullah, Bergström, astro-ph/0404468
prior on M 15
Theoretical systematics
Test: simulate + fit 500 experiments , z-distribution and
uncertainties as in Tonry + Barris et al
cosmology
Metamorphosis
not needed to
explain the fits!
”Transition
redshift” set by
Jönsson, AG, Amanullah, Bergström, astro-ph/0404468
prior on M 16
Theoretical systematics
Test: simulate + fit 500 experiments , z-distribution and
uncertainties as in Tonry + Barris et al
cosmology
Metamorphosis
not needed to
explain the fits!
”Transition
redshift” set by
Jönsson, AG, Amanullah, Bergström, astro-ph/0404468
prior on M 17
Major ongoing/future SN programs
• Low redshift: starting in 2004
Carnegie Supernova Project ~200 SN1a with z<0.07´(UBVRIJHK)
SuperNova Factory ~300 SN1a z<0.08
• Intermediate redshift: starting 2005(?)
SLOAN ~300 0.1<z<0.4
• High-z
SNLS: 2003-2008; 700 SNe 0.3<z<0.9
ESSENCE:2002-2005; 200 SNe 0.2<z<0.7
• Very High-z (z>1) 2003-2005
PANS/GOODS + SCP: ~50 (1 < z < 2)
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Dark Energy statistical precision from CFHT
Legacy Survey
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Dark Energy and Dark Matter.
- Long term future Supernova Project
SNAP/JDEM satellite:
several thousend very
high-z Sne/year + weak
lensing survey
~2-meter mirror 0.7•° FOV
imaging + spectroscopy
0.35-1.7 mm,
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The Next Generation: SNAP/JDEM – good
controll of systematics
SNAP
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SNAP: probing Dark Energy models
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SNAP precision on w’
Planck data
provides
complementarity
equal to a prior
(M)0.01.
Frieman, Huterer,
Linder, Turner 2002
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SNAP: Weak Gravitational Lensing
Distortion of background images by foreground matter
Credits: R.Ellis
Unlensed
Lensed
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SNe + Weak Lensing (cf A.Taylor)
Bernstein, Huterer, Linder, & Takada
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• Comprehensive:
no external priors
required!
• Independent test of
flatness to 1-2%
• Complementary:
w0 to 5%, w to
0.11 (with
systematics)
Summary & Conclusions
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Quite healthy 6 year old! Evidence for DE
seems robust w.r.t identified systematic
effects..
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is Dark Energy=?
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No convincing evidence against it!
stat ~ syst → need better quality data to
make use of large statistics to come…
New very high-z from ground and space
extremely exciting but sytematics not yet
fully studied.
Large number of ongoing projects will
provide several hundreds (thousends?) of
nearby and distant supernovae.
SNAP/JDEM a very exciting mission with
capability of resolving the DE mysteri...but
launch in 2014???
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