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Dark Energy and Supernovae
Wendy Freedman
Carnegie Observatories, Pasadena CA
Beyond Einstein, SLAC, May 13, 2004
Understanding Dark Energy
Talks at this meeting
Type Ia Supernovae for
Cosmology
Riess et al. 1998
Perlmutter et al. 1999
First evidence for
acceleration
Type Ia Supernovae for
Cosmology
Advantages:
• small dispersion
• single objects (simpler than galaxies)
• can be observed over wide z range
Challenges:
• dust (grey dust)
• chemical composition
• evolution
• photometric calibration (e.g., Vega)
• environmental differences
Systematics
• lensing
Step 2
Type Ia supernovae as distance
indicators
Luminosity Distances
Characterizing the Equation of
State
Finding Supernova Candidates
High z Supernova Team
Supernova Spectra
Type Ia SN diagnostics
(restframe):
• Si II – 4130 A
• Ca II – 3950 A
• Fe blends
Perlmutter et al.
1998
Spectra of Supernovae
Even without spectra,
colors turn out to be
an extremely effective
means of distinguishing
Type Ia and II supernovae.
Riess et al. 2004
Type II
Type I
State of the Art
Knop et al. 2003
State of the Art
Knop et al. 2003
State of the Art
• HST ACS data
Riess et al. 2004
177 supernovae; 7 new
objects 1.25 < z < 1.8
Evidence for deceleration
at earlier matter-dominated
epoch.
GOODS/ACS Supernova Candidates
Riess et al. 2004
GOODS / ACS Light Curves &
Spectra
Riess et al. 2004
Constraints on Equation of State
Riess et al. 2004;
Knop et al. 2003
Assuming: m = 0.27 § 0.04
Corrections for reddening, metallicity,
evolution well-understood
w0 = -1.05 § 0.2 § 0.1
Equation of State and Dark Matter
Density : Combined Constraints
Assume flat universe
Consistency with
cosmological constant
w = -1
Tegmark et al (2004)
Does the Dark Energy Density
Vary with Time?
Wang & Tegmark (2004)
Recall Assumptions:
• flatness
• m = 0.3 § 0.04
2004 Standard Cosmological Model
A universe with a flat geometry composed
of one third matter density, and two
thirds dark energy.
m = 0.3
L = 0.7
0 = 1
h = 0.7
w = -1
dw/dz = 0
Minimizing Systematics
in era of precision cosmology
Grey Dust?
There is no
evidence to
date for gray
dust.
Riess et al. 2004
The data are
consistent
with the
presence of
dark energy.
Galactic Extinction Law
U
B
AU / E(B-V) = 4.9
AB / E(B-V) = 4.1
V
I
AI / E(B-V) = 1.7
R V = AV / E(B-V)
Cardelli, Clayton and Mathis 1989
E(B-V) Distributions for SN1a
Knop et al. 2003
Supernova Ia Metallicities
•Lower fluxes for
higher metallicity
•Variation in level
of UV continuum
UV
.03 x solar
10x solar
Lentz et al. 1999 models
optical
IR
Goals
SNAP:
• measurement of w to 5%
• measurement of w’ to 12%
• Joint constraints with weak lensing
• L (better for SUGRA)
Present/Future Supernova
Projects
High z:
• CFHT Legacy Survey
• ESSENCE
• Carnegie Supernova
Project (CSP)
•Supernova Cosmology
Project (SCP)
•GOODS
Future Supernova
Projects:
Low z:
• LOTOSS (KAIT)
• SN Factory
• CSP
• LSST, Panstarrs
• Giant Magellan
• SNAP
• DESTINY
Ground-based supernova searches
over next 5 years
- 100s of supernovae
- decreasing systematics
CFHT Legacy Survey (SNLS)
• ugriz light curves
• observations to I’ ~ 28 mag
• CFHT MegaCam
• 2000 SN over 5 years
• 0.1 < z < 1
ESSENCE
•VRI light curves
• CTIO 4m Mosaic Imager
• 200 SN over 5 years
• share nights with
Supermacho project
• observe each field every
4 nights
• 0.1 < z < 0.8
High z Supernova Team
NOAO Science Archive:
http://archive.noao.edu/nsa/
LOTOSS / KAIT
• Automated supernova search
•UBVRI light curves
• Lick Observatory
• 0 < z < ~0.15
Supernova Factory
2002: 35 candidates
• spectrophotometry
• Univ. Hawaii
• 0.32 – 1 m
• NEAT, Palomar (search)
• ~150 SNae per year
• 3 years
Wood – Vasey et al 2004
Same search techniques as distant searches
Followup supernova projects
The Carnegie Supernova
Project (CSP)
A restframe I-band Hubble
diagram
Carnegie Supernova Project (CSP)
Why an I-band Hubble diagram?
• Advantages:
- dust
- chemical composition
- low dispersion
=> reduce systematics
[Why hasn’t this been done? HARD! IR detectors on large telescopes]
Wavelength-Redshift Coverage
CSP:
• 0<z<0.2
comparison
UBVRIJHK
HST
Essence
CFHTLS
CSP
CSP
• 0.3<z<0.8
VRI restframe
HST:
• 0.5<z<1.5
• UBV(R)
restframe
Overview of Carnegie Supernova Project
Swope 1-meter
Low z:
Dupont 2.5-meter
Magellan 6.5-meter
High z:
•u’BVr’I’YJH photometry
• Dupont spectroscopy
• r’i’YJ photometry
• Magellan spectroscopy
• C40 9 month campaigns
over 5 years
• densely sampled photometry
and spectroscopy 0 < z < 0.2
• SNIa and SNII
• ~200 nights over 5 years
• ~200 SNIa
• 0.2 < z < 0.8
Carnegie Supernova Project
Goals:
• minimize systematics
• accurate reddenings,
K-corrections
• H0 (H-band observations
for Cepheids + SNIa)
• dark energy
• peculiar flows
• physics of SNI and II
Magellan
PANIC
Jha 2002
Carnegie Supernova Project
Recent results on
Nearby supernovae:
• ~30 observed to date
• UBVRIJHK light curves
• excellent sampling
Krisciunas et al. (2002)
SN2001el
Carnegie Supernova Project
• decline rate versus magnitude
• BVIH
• H-band promising as
distance indicator
Krisciunas et al.
Carnegie Supernova Project
• decline rate versus
magnitude
JHK
Krisciunas et al. (2004)
JHK Hubble diagrams
Extinction-corrected apparent
magnitude at maximum
Carnegie Supernova Project
Redshift in CMB frame (km/sec)
Krisciunas et al.
Future supernova projects
- 1000s of supernovae
- similar precision at
high redshifts to upcoming
low redshift surveys
- decreased systematics
Large Synoptic Survey Telescope
(LSST)
•Highly ranked in Decadal
Survey
•Optimized for time domain
•7 square degree field
•6.5m effective aperture
•24th mag in 20 sec
•15 TBytes/night
(current ESSENCE
20 GBytes/night)
•Real-time analysis
Panstarrs
Future Plans (Carnegie High z)
The Giant Magellan Telescope (GMT)
•
•
•
•
•
Roger Angel mirrors
Seven 8.4-meter mirrors; f/0.7
21.5-meter aperture, 25.3-meter baseline
A consortium of partners currently
including Carnegie, Harvard/Smithsonian,
University of Arizona, MIT, and the
University of Michigan *
Funds are in place for the 18-month
conceptual design phase
Highest Priority Capabilities:
1. Narrow field, high dynamic range AO
2. Wide field, optical spectroscopy
Dark Matter (lensing) and dark energy studies.
Supernovae 1<z<2
Magellan
HST Treasury (Large)
Proposals (Cycle 13)
• Riess et al. :
Double high z sample
• Filippenko et al. :
UV nearby survey
Future Surveys (Space): JDEM
SNAP
DESTINY: Dark Energy
Space Telescope
SNAP focal plane
SNAP Target Precision
Current Status of Cosmological
Parameter Measurements
• WMAP (+ one of
H0 , LSS, SNae) is
consistent with a
FLAT universe
Wright, 2004
• Consistent model
with h = 0.72
m = 0.27
L = 0.73
w = -1