The Five stages of SDSS: 1. Denial 2. Anger 3. Bargaining...
Transcript of The Five stages of SDSS: 1. Denial 2. Anger 3. Bargaining...
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Stages of a Big Project***
The Five stages of SDSS:
1. Denial2. Anger3. Bargaining4. Depression5. Acceptance
*** With apologies to Elizabeth Kubler Ross
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The Carnegie Supernovae Project
Wendy Freedman Carnegie Observatories
SDSS: From Asteroids to CosmologyChicago, August 18, 2008
Wendy Freedman Carnegie Observatories
SDSS: From Asteroids to CosmologyChicago, August 18, 2008
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Supernovae Prior to SDSS-II
Intermediate redshift desert
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SNe Ia and Cosmology: State of the Art
Riess et al. 2004
HST ACS data
Knop et al. 2003 Astier et al. 2006
Wood-Vasey et al. 2007 WLF et al. 2008
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Type-Ia Supernovae
• Progenitor is a white dwarf accreting material from a binary companion.
• As the white dwarf approaches the Chandrasekhar mass, a thermonuclear runaway is triggered.
• “Standardizable candles”
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Type-Ia Supernovae (con’t)
• Rise time: ~ 20 days• Decay time: ~ 2 months• Brightness: MB ~ –19.5 at peak• Found in all types of galaxies
Spectral Classification:
No hydrogen in the spectra
Early spectra: Si, Ca, Mg (absorption features)
Late spectra: Fe, Ni (emission features )
Type Ia
Type Ic
.
Si II
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Caveats for Supernovae and the determination of w
I. A very wide range of w and H0combinations are consistent with the current CMB and supernova data. There is a severe degeneracy between w or ΩΛ and H0.
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WMAP: Relax Constraint of Flat Universe
Range of non-flatmodels consistentwith WMAP data
Dashed lineΩk = -0.3 + 0.4 ΩΛ
Spergel et al. 2006
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Caveats for Supernovae and the determination of w
II. The determination of w from supernovae alone requires the assumption of a flat Universe.
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SNe alone can’t measure w
Model with w = -1 and w = -0.9 agree to within ± 2 millimag, after adjusting Ωm, ΩΛ and M (the absolute magnitude or Hubble constant)
Slide due to Ned Wright
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SNe alone can’t measure w’
Model with w’ = 0 and w’ = -0.1 agree to within ± 1 millimag
Slide due to Ned Wright
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Type Ia Supernovae for Cosmology
Advantages:• small dispersion • direct measure of acceleration • can be observed over wide z range • straightforward empirical tests of systematics
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Systematic Treatment
Dust extinction
Multi-band photometry including near-IR
Evolution High-resolution spectroscopy
Photometric calibration
New calibration of standard stars optical through near-IR to <1% accuracy
Malmquist bias
High S/N light curves and spectra; requirement of pre-rise data
K-corrections Library of supernova spectra with broad wavelength, temporal and Δ m15 coverage.
Lensing Measure the average flux for a large number of supernovae in each redshift bin.
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Dark Energy Task Force Report: Albrecht et al.SN-II700 SNe500 nearby
SN-III spectra2000 SNe
SN-IV LSST
pessimistic
optimistic
300,000 SNeSN-IVspace2000 SNe
w = -1ΩΛ = 0.73
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DETF Forecast: Combining Techniques
Stage II
Stage IV BAO+SN+WL (P and O)
space
Contours 95% CL
Albrecht et al. 2006Note: all same priors
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Carnegie Supernova Project: Primary Goals
1. I-band restframe Hubble diagramObservations in the near-IR (>1μm)
“Y” , J bandsTo date only UBV restframe…
2. Reduce systematics (reddening, calibration, K-corrections…)Multi-wavelength observations
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Carnegie Supernova Project
Swope 1-meter Magellan 6.5-meterDupont 2.5-meter
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Carnegie Supernova Project
Swope 1-meter Magellan 6.5-meterDupont 2.5-meterLow z: High z:
•u’BVg’r’i’YJHK photometry• 2.5-meter spectroscopy
• YJ photometry• Magellan 6.5-meter
• ~75 SNe Ia at completion• observations near max• 0.2 < z < 0.7
• C40 9 month campaignsover 5 years (1350 nights)
• densely sampled photometryand spectroscopy 0 < z < 0.1
• 100 SNe Ia, 100 SNe II
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Carnegie Supernova Project (CSP)
Chris BurnsCarlos ContrerasGaston FolatelliWendy Freedman (PI, High z)Mario HamuyBarry MadoreNidia MorellEric PerssonMark Phillips (PI, Low z)Miguel RothMax StritzingerNick Suntzeff
Collaborators:Ray Carlberg, Chris Pritchet, Mark
Sullivan, Kathy Perrett, AndyHowell (CFHT SN Legacy)
Alex Filippenko, Weidong Li (LOSS)Nick Suntzeff (ESSENCE)Josh Friemann (SDSS-II)
Dan Kelson, Eric Hsiaohttp://www.ociw.edu/csp/
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Corrections for Dust Extinction
Cardelli, Clayton and Mathis 1989
B
I
V
R V = AV / E(B-V)U
Complications:
• Several potential sources:(MW, host, circumstellar,IGM)
• Intrinsic color vs reddeningdegeneracy
• low z:<E(B-V)> = 0.12 ± 0.14
• high z:<E(B-V)> = 0.06 ± 0.13
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Reddening / Intrinsic Color• Current largest systematic effect • Degeneracy between reddening and intrinsic color
CSP: Two independent approaches1. Solve for individual reddenings using
“unreddened” sample (Phillips et al. 1999)
2. Use a “reddening-free magnitude, ww = i Rλ (B-V) = i0 Rλ (Β-V)0 Folatelli et al. 2009
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Improved K-corrections• 125 spectra
covering I band
• match spectraltemplates to observed colors
• uncertaintiesrange from ± 0.005 to ± 0.1mag
CSP {
Ca triplet
Hsiao et . al astro-ph 0703529
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CSP Approach
• Internal double-blind tests
photometric zero pointsgalaxy template subtractionlight-curve templatesdecline-rates, max light magnitudesreddenings
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Other Effects
• Spiral galaxies host slower(and more luminous) SNe Ia
• The scatter in the Hubblediagram is a function ofgalaxy type (lower for E’s)
• Effect of metallicity andenvironment on cosmologyappears to be smallLocal Template
Mean High z
UVSpectra
Sullivan et Sullivan et
al. (2003)al. (2003)
Ellis et Ellis et
al. (2007)al. (2007)
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• CFHT Legacy Survey • ESSENCE
CSP Collaborations
• LOTOSS (KAIT)• SN Factory
High z:
Low z:
Intermediate z:• SDSS-II
CSP follow-up and collaboration
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The Low-z CSPPI: Mark Phillips
SN2006X
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Sources for Low-z SupernovaeLOSS + many others
CSP Low z Target Sample:
100 SNe Ia100 SN II25 SN Ibc
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Low-z SNe Ia: Optical Light Curves
Δm15(B)
0.90
1.83
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Examples of CSP Low-z Light Curves
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• SN 2006X• NGC 4321
(M100)•Spectra from
du Pont andMagellan /LDSS2
Carnegie Supernova Project Low-z
Nidia MorellSN2006X
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• 20 well-observed SNe Ia• Folatelli, Phillips et al. (in prep.)• WLF, Sturch, Madore, Burns et al. (in prep.)
Absolute MagnitudeVersus Decline Rate
BV Hubble Diagrams
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Carnegie Supernova Project: High z
SNLSSDSS-IIESSENCE
Redshift z
• 74 SN Iaobserved with0.11 < z < 0.70
• 56 with at leastone template
23 withcompletereductions,reddenings
Num
ber
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Carnegie Supernova Project: High zExample i’-bandlight curves: low z
• Observe pre-maximum
• Follow 3-7epochs
Less than 10days aftermaximum
• Gaps less than5 days
1st peak
2nd peak
CSP1.8
1.1
High z:
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Carnegie Supernova Project: High z
z = 0.59
z = 0.52
i
r
i
JY
Templatelight curvesbased on low-redshiftCSP data.
I-band (YJ)photometryfrom Magellan
Optical BVRphotometryfrom:SNLSESSENCESDSS-II
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Carnegie Supernova Project: High z
z = 0.59
z = 0.52
i
r
JY
I-band (YJ)photometryfrom Magellan
Optical BVRphotometryfrom:SNLSESSENCESDSS-II
e.g.,Magnitudeuncertainties
<Y> z±0.03 0.1-0.3±0.06 0.3-0.5±0.08 0.5-0.7
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CSP Template Light Curves
i
CSP Low z example light curves:use for templates
rV
Bu
g
B. Madore
Light curve parameters:
Determine Δ m15 – declinerate values and time of maxusing χ2 minimization
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Carnegie Supernova ProjectCSP data:
23 Type Ia supernovae0.18 < z < 0.68
24 Type Ia supernovae0.01 < z < 0.07
First I-bandHubble diagramat z > 0.07
WLF et al. (2008)
i ‘- band
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Carnegie Supernova Project: High z
CSP + BAO data:Eisenstein et al. 2005
ΩDE > 0 at a >>3-σconfidence level.
ΩDE = 0.72 ± 0.08 (stat)± 0.05 (sys)
CSP
BAO
Joint constraints
Assumptions:w = -1wa = 0
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Carnegie Supernova Project: High z
Joint constraintsCSP+BAO(Eisenstein 2005):
ΩM = 0.28 ± 0.02 (stat)w0 = -1.01 ± 0.09 (stat)
± 0.08 (sys)
Systematic errors included
CSP
BAO
W0
ΩM
BAO
CSP
Assume flatness
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Summary of Cosmological Parameters
Future: 100 SNe Ia (low z)75 SNe Ia (high z)
Comparable uncertainties to other optical surveys oflarger sizes due to smaller systematic uncertainties.
Currently ~1/3 offinal sample
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