Stages of a Big Project***

The Five stages of SDSS:

1. Denial2. Anger3. Bargaining4. Depression5. Acceptance

*** With apologies to Elizabeth Kubler Ross

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

Supernovae Prior to SDSS-II

Intermediate redshift desert

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

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”

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

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.

WMAP: Relax Constraint of Flat Universe

Range of non-flatmodels consistentwith WMAP data

Dashed lineΩk = -0.3 + 0.4 ΩΛ

Spergel et al. 2006

Caveats for Supernovae and the determination of w

II. The determination of w from supernovae alone requires the assumption of a flat Universe.

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

SNe alone can’t measure w’

Model with w’ = 0 and w’ = -0.1 agree to within ± 1 millimag

Slide due to Ned Wright

Type Ia Supernovae for Cosmology

Advantages:• small dispersion • direct measure of acceleration • can be observed over wide z range • straightforward empirical tests of systematics

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.

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

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

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

Carnegie Supernova Project

Swope 1-meter Magellan 6.5-meterDupont 2.5-meter

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

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/

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

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

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

CSP Approach

• Internal double-blind tests

photometric zero pointsgalaxy template subtractionlight-curve templatesdecline-rates, max light magnitudesreddenings

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)

• CFHT Legacy Survey • ESSENCE

CSP Collaborations

• LOTOSS (KAIT)• SN Factory

High z:

Low z:

Intermediate z:• SDSS-II

CSP follow-up and collaboration

The Low-z CSPPI: Mark Phillips

SN2006X

Sources for Low-z SupernovaeLOSS + many others

CSP Low z Target Sample:

100 SNe Ia100 SN II25 SN Ibc

Low-z SNe Ia: Optical Light Curves

Δm15(B)

0.90

1.83

Examples of CSP Low-z Light Curves

• SN 2006X• NGC 4321

(M100)•Spectra from

du Pont andMagellan /LDSS2

Carnegie Supernova Project Low-z

Nidia MorellSN2006X

• 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

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

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:

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

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

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

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

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

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

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