PS1 Type Ia Supernovaeifa.hawaii.edu/users/chambers/ps1sc/PS1SC_Meeting_Jan... · 2012. 1. 5. ·...

PS1 Type Ia Supernovae

Ryan FoleyClay FellowHarvard-SmithsonianCenter for Astrophysics

Armin RestDan ScolnicRyan ChornockMark HuberGautham NarayanSteve RodneyJohn Tonry

White Dwarf inBinary System

Accretes MatterUntil ~1.4 timesthe Mass of theSun

Explodes and isVery, VeryLuminous

SNe Ia Are Exploding White Dwarfs

SNe Ia Are Standardizable CandlesFaint = Fast, Red

Bright = Slow, Blue

σ = 0.18 mag

“Single Parameter”

Type Ia Supernovae as Standard Candles 7

Fig. 1.4.— Optical light curves of 53 SNe Ia. The light curves are color-codedby ∆, a unitless parameter that describes the light-curve shape. Larger valuesof ∆ correspond to narrower light curves. From M. Ganeshalingam, privatecommunication.

Ganeshalingam et al. 2011a

FB

σ = 0.44 mag

σ = 0.18 mag!

Calibrating SNe Ia

71

0.0 0.2 0.4 0.6 0.8 1.0redshift

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1d

iffe

ren

ce

in

dis

tan

ce

mo

du

lus

empty

!m=1

!m=0.3

w=-1.1

w=-0.9

Figure 4.1: Difference in distance modulus, as a function of redshift, for variouscosmologies relative to the current “consensus” cosmology (Ωm = 0.3, ΩΛ = 0.7).The black curves show differences in distance modulus as a function of redshift forcosmologies without dark energy, while the blue curves indicate the difference foruniverses with the same densities as the “concordance” universe, but whose values ofw differ by 10% from that of a cosmological constant.

able source of systematic error impacts our measurements and tabulate an appropriate

error budget.

The “signal chain” which takes raw digital images from the telescope through to

measurements of brightness to estimated distances and finally to cosmological pa-

rameters, is complex, with the potential for interplay between many subtle effects.

Rather than attempting to recreate this chain using Monte Carlo simulations to pro-

duce mock data sets, we have elected to estimate systematics by subjecting our actual

measurements to perturbations which mimic expected sources of systematic error. By

exaggerating each effect, we effectively measure dw/ds, the change in the equation

of state parameter in response to a systematic effect s. Then, by establishing some

estimate of the magnitude, δs, of each effect, we derive its contribution to the sys-

Measuring w is Hard

Recent Hubble Diagram

35

40

45d

ista

nce m

od

ulu

s [

mag

]M

LC

S2k2

CfA3: Hicken et al. (2009)

Calán/Tololo: Hamuy et al. (1996)

CfA1: Riess et al. (1999)

CfA2: Jha et al. (2006)

SDSS: Kessler et al. (2009)

ESSENCE: Wood!Vasey et al. (2007)

SNLS: Astier et al. (2006)

HST: Riess et al. (2007)

redshift

!0.4

!0.2

0.0

0.2

0.4

resid

ual [m

ag

]

0.01 0.02 0.05 0.1 0.2 0.5 1.0 2.0

The Astrophysical Journal Supplement Series, 192:1 (29pp), 2011 January Conley et al.

Table 7Identified Systematic Uncertainties

Description Ωm w Rel. Area a w for Ωm = 0.27 Section

Stat only 0.19+0.08−0.10 −0.90+0.16

−0.20 1 −1.031 ± 0.058

All systematics 0.18 ± 0.10 −0.91+0.17−0.24 1.85 −1.08+0.10

−0.11 Section 4.4

Calibration 0.191+0.095−0.104 −0.92+0.17

−0.23 1.79 −1.06 ± 0.10 Section 5.1

SN model 0.195+0.086−0.101 −0.90+0.16

−0.20 1.02 −1.027 ± 0.059 Section 5.2

Peculiar velocities 0.197+0.084−0.100 −0.91+0.16

−0.20 1.03 −1.034 ± 0.059 Section 5.3

Malmquist bias 0.198+0.084−0.100 −0.91+0.16

−0.20 1.07 −1.037 ± 0.060 Section 5.4

Non-Ia contamination 0.19+0.08−0.10 −0.90+0.16

−0.20 1 −1.031 ± 0.058 Section 5.5

MW extinction correction 0.196+0.084−0.100 −0.90+0.16

−0.20 1.05 −1.032 ± 0.060 Section 5.6

SN evolution 0.185+0.088−0.099 −0.88+0.15

−0.20 1.02 −1.028 ± 0.059 Section 5.7

Host relation 0.198+0.085−0.102 −0.91+0.16

−0.21 1.08 −1.034 ± 0.061 Section 5.8

Notes. Results including statistical and identified systematic uncertainties broken down into categories. In each case, the constraintsare given including the statistical uncertainties and only the stated systematic contribution. The importance of each class of systematicuncertainties can be judged by the relative area compared with the statistical-only fit.a Area relative to statistical-only fit of the contour enclosing 68.3% of the total probability.

0.0 0.3 0.6 0.9 1.2 1.5z

−0.01

0.00

0.01

∆ m

B

0.0 0.3 0.6 0.9 1.2 1.5z

−0.01

0.00

0.01

∆ C

−0.01

0.00

0.01

∆ s

−0.05

0.00

0.05

∆ m

corr

Figure 7. Effects of changing the iM zero point by 6.1 mmag on various light-curve parameters and the corrected peak magnitude mcorr = mB +α (s − 1)−βC,as a function of redshift. Note that because this affects our SN models (SALT2and SiFTO), as the training sample includes SNLS data, this alters the correctedpeak magnitudes of all SNe, not just those in the SNLS sample. Furthermore,because of the changes in the light-curve model, the offset in the derived colorcan actually be larger than the shift in the zero point.(A color version of this figure is available in the online journal.)

the BAO and WMAP constraints, which mostly improve themeasurement by constraining Ωm. In both cases, we comparethe uncertainties on the cosmological parameters from a fit thatonly includes statistical uncertainties with one that includesstatistical uncertainties plus only that systematic term. Wealso provide the relative size of the contour that encloses68.3% of the probability, compared with the statistical-onlycontours. This is similar in spirit to the Dark Energy TaskForce figure of merit (Albrecht et al. 2006), and is perhapsthe simplest way of expressing the importance of each term.Because of the curvature of the SN-only constraints, the area ofthe inner contour can actually increase while the marginalizeduncertainties decrease. We caution against the practice ofcomparing the shifts in the best fit as a useful method ofmeasuring systematic effects, as it can be misleading. Anupdated version of the effects on the cosmological parameters isgiven in S11 combined with external constraints such as baryonacoustic oscillations and CMB measurements. An example ofthe effects of one systematic (the iM SNLS zero point, discussed

0.0 0.2 0.4 0.6 0.8 1.0Ωm

0.0

0.5

1.0

1.5

ΩΛ

99.7%

99.7%

99.7%

95.4%

95.4%

68.3%

Accelerating

Decelerating

No big bang

Figure 8. Ωm, ΩΛ (i.e., w = −1, but allowing for non-zero spatial curvature)contours including all identified systematic uncertainties.(A color version of this figure is available in the online journal.)

in Section 5.1.1) on the light-curve parameters as a function ofredshift is shown in Figure 7.

4.4. Combined Statistical and Systematic Results

Including all identified systematic effects, the results foran Ωm, ΩΛ fit are shown in Figure 8. The SN data alonerequire acceleration at high significance. The results for a flatuniverse with a constant dark energy equation of state aresummarized in Table 6, and the contours are shown in Figure 9.We find w = −0.91+0.16

−0.20 (stat)+0.07−0.14 (sys), again consistent with

a cosmological constant. An overview of the importance ofeach class of systematic effect is given in Table 7—calibrationeffects are by far the dominant type of identified systematicuncertainty. Overall, the systematic uncertainties degrade thearea of the uncertainty ellipse by a bit less than a factor of tworelative to the statistical-only constraints. Excluding the SDSSand CSP SNe (calibrated to a USNO system) increases the areaof the uncertainty ellipse by about 10%; the improvement fromincluding this data should be increased once the full benefits ofcross calibrating these two samples with SNLS are realized.

It is interesting to compare the constraining power of thelow-z, SDSS, and SNLS samples. This was also explored in

14

Supernovae Only (with Systematics)

Conley et al. 2011


0.0 0.1 0.2 0.3 0.4 0.5Ωm

−2.0

−1.5

−1.0

−0.5

w99.7%

99.7%

99.7%

99.7%

95.4%

95.4%

95.4%

68.3%

68.3%

Figure 9. Constraints on Ωm,w in a flat universe including all identifiedsystematic uncertainties.(A color version of this figure is available in the online journal.)

No SDSS

0.0 0.1 0.2 0.3 0.4 0.5Ωm

−3.0

−2.5

−2.0

−1.5

−1.0

−0.5

w

No Low−z

0.0 0.1 0.2 0.3 0.4 0.5Ωm

No SNLS

0.0 0.1 0.2 0.3 0.4 0.5Ωm

Figure 10. Comparison of the constraints on Ωm, w in a flat universe excludingvarious samples. First, in the left panel, we exclude the SDSS sample (sothe included samples are SNLS, HST, and low-z), in the middle the low-zsample, and on the right the SNLS data. The fits include all identified systematicuncertainties. The filled contours are the constraints with all samples, and thedashed contours exclude the labeled sample.(A color version of this figure is available in the online journal.)

K09, but with a smaller low-z sample (33 versus 123 SNe).The resulting constraints without each sample are shown inFigure 10; as can be seen, the first year of SDSS data is nota good replacement for the nearby sample, although the fullthree year sample may alter this situation. Excluding the SNLSsample has a significant negative impact on the cosmologicalconstraints.

4.5. Tension Between Data Sets

As a test of whether our estimates for systematic effects arereasonable, we compute the mean offsets in the residuals fromthe cosmological fit between different samples. We computethe weighted mean residual for each sample, including thestatistical and systematic covariance matrices and assumingthe best-fit values of α and β. The results are summarized inTable 8 and show no significant evidence for any disagreementbetween samples (the apparent increase with z is not statisticallysignificant). Note that our estimates for each systematic termwere constructed before this test was carried out. We have alsocompared the rms around the best fit for different sources of the

Table 8Tension Between Different SN Samples

Sample Mean Offset (mag) Uncertainty N

Low-z −0.027 0.024 123SDSS 0.020 0.027 93SNLS 0.023 0.023 242HST 0.043 0.072 14

Calan/Tololo −0.027 0.046 17CfAI 0.064 0.062 7CfAII 0.051 0.049 15CfAIII −0.047 0.034 58CSP 0.052 0.057 14Other 0.052 0.057 12

low-z sample. Generally, these are consistent, with the exceptionof the CfAII sample (which has an rms of 0.20 mag, comparedwith 0.153 mag for the other samples). This is mostly dueto a single SN which just barely passes our outlier rejection,SN 1999dg. Without this SN, the rms of the CfAII sample is0.163 mag. The CfAI, CfAIII, and CSP samples show slightlybelow average rms (about 0.14 mag), but this is not statisticallysignificant. Note that the relative weights of the samples in thiscomparison should not be taken too seriously because of thesomewhat arbitrary way in which systematics were attributedto particular samples, although test for tension is meaningful.Specifically, the systematic uncertainties in the cross-calibrationbetween the low-z and other samples are always assigned tothe latter (SDSS, SNLS, etc.) which decreases their apparentweight; it would be just as valid to assign the cross-calibrationuncertainties to only the low-z sample, which would make theother samples appear to have much more weight. The actualweights should be judged in terms of the consequences ofremoving each sample, as in Figure 10.

4.6. The Consequences of Simplified Treatments

In this section, we describe the consequences of varioussimplifying assumptions in the analysis. Figure 11 shows theeffects of not including uncertainties related to the light-curvemodels, specifically omitting the model statistical uncertaintyand the effects of the systematic effects on the model training.The consequences are not as severe as the effects of fixing thenuisance parameters, but still will obviously underestimate theuncertainties. The general effects are to underestimate the totaluncertainty budget, although the size of the effect depends onthe simplification.

α and β are correlated with the cosmological parameters, withcorrelation coefficients of about 0.2 for the Ωm,w fit; droppingthe assumption of flatness or investigating time varying wgenerally increases these correlations. Therefore, the treatmentsometimes found in the literature of fixing α and β at their best-fit values and not fitting for them explicitly both underestimatesthe uncertainties and results in biased parameter estimates.A related simplification is allowing α and β to vary for thestatistical uncertainty (Dstat of Equation (5)), but holding it fixedwhen computing the systematics, as in Kowalski et al. (2008)and Amanullah et al. (2010). This simplification also biases αand β, and therefore the cosmological parameters, as shownin the right-hand panel of Figure 11, and underestimates theuncertainties; for this sample, it amounts to underestimating thesize of the inner uncertainty contour by ∼40%, although theeffects on the marginalized uncertainties are modest.

15

Conley et al. 2011

Supernovae Only (with Systematics)

w = −0.91 ± 0.18 (stat) ± 0.11 (sys)

The Astrophysical Journal, 737:102 (19pp), 2011 August 20 Sullivan et al.

0.0 0.1 0.2 0.3 0.4 0.5Ωm

−2.0

−1.5

−1.0

−0.5

w

99.7%

95.4%

68.3

%

SNLS3

BAO+WMAP7

With all systematics

0.0 0.1 0.2 0.3 0.4 0.5Ωm

−2.0

−1.5

−1.0

−0.5w 99.7%

95.4%

SNLS3

BAO+WMAP7

Statistical only

0.0 0.1 0.2 0.3 0.4 0.5Ωm

−2.0

−1.5

−1.0

−0.5

w 99.7%

95.4%

SNLS3

BAO+WMAP7

With systematicsexcl. "calibration"

0.0 0.1 0.2 0.3 0.4 0.5Ωm

−2.0

−1.5

−1.0

−0.5

w

SNLS3

BAO+WMAP7

With systematics,Fixing α, β

Figure 2. Confidence contours in the cosmological parameters Ωm and w arising from fits to the combined SN Ia sample using the marginalization fitting approach,illustrating various systematic effects in the cosmological fits. In all panels, the SNLS3 SN Ia contours are shown in blue and combined BAO/WMAP7 constraints(Percival et al. 2010; Komatsu et al. 2011) in green. The combined constraints are shown in gray. The contours enclose 68.3%, 95.4%, and 99.7% of the probability,and the horizontal line shows the value of the cosmological constant, w = −1. Upper left: the baseline fit, where the SNLS3 contours include statistical and allidentified systematic uncertainties. Upper right: the filled SNLS3 contours include statistical uncertainties only; the dotted open contours refer to the baseline fit withall systematics included. Lower left: the filled SNLS3 contours exclude the SN Ia systematic uncertainties related to calibration. Lower right: the filled SNLS3 contoursresult from fixing α and β in the cosmological fits. See Tables 2 and 3 for numerical data.(A color version of this figure is available in the online journal.)

We then present our main cosmological results. We investi-gate a non-flat, w = −1 cosmology (fitting for Ωm and ΩΛ),a flat, constant w cosmology (fitting for Ωm and w), a non-flat cosmology with w free (fitting for w, Ωm, and Ωk), and acosmology where w(a) is allowed to vary via a simple linearparameterization w(a) = w0 + wa(1 − a) ≡ w0 + waz/(1 + z)(e.g., Chevallier & Polarski 2001; Linder 2003), fitting for Ωm,w0, and wa . We always fit for α, β, and MB .

The confidence contours for Ωm and w in a flat universecan be found in Figure 2 (upper left panel) for fits consideringall systematic and statistical uncertainties. Figure 2 also showsthe statistical-uncertainty-only cosmological fits in the upperright panel. The best-fitting cosmological parameters and thenuisance parameters α, β, M1

B , and M2B , for convenience

converted to MB assuming H0 = 70 km s−1 Mpc−1 (in thegrid marginalization approach, H0 is not fit for as it is perfectlydegenerate with MB), are in Table 1 (for non-flat, w = −1 fits)and Table 2 (for flat, constant w fits). We also list the parametersobtained with the χ2 minimization approach for comparison. Allthe fits, with and without the inclusion of systematic errors, are

consistent with a w = −1 universe: we find w = −1.043+0.054−0.055

(stat) and w = −1.068+0.080−0.082 (stat+sys). For comparison, with

no external constraints (i.e., SNLS3-only) the equivalent valuesare w = −0.90+0.16

−0.20 (stat) and w = −0.91+0.17−0.24 (stat+sys) (C11).

The lower right panel of Figure 2 shows the importance ofallowing the nuisance parameters α and β to vary in the fits,rather than holding them fixed at their best-fit values. Thisleads to not only smaller contours and hence underestimatedparameter uncertainties, but also a significant bias in the best-fit parameters (Table 3). Holding α and β fixed gives w =−1.117+0.081

−0.082, a ∼0.6σ shift in the value of w compared to thecorrect fit.

The residuals from the best-fitting cosmology as a functionof stretch and color can be found in Figure 3. No significantremaining trends between stretch and Hubble residual areapparent, but there is some evidence of a small trend betweenSN Ia color and luminosity at C < 0.15 (indicating that theseSNe prefer a smaller β, or a shallower slope, than the globalvalue). We examine this, and related issues, in more detail inSection 5.

7

Constraints on w

Sullivan et al. 2011

The Astrophysical Journal, 737:102 (19pp), 2011 August 20 Sullivan et al.

0.0 0.1 0.2 0.3 0.4 0.5Ωm

−2.0

−1.5

−1.0

−0.5w

99.7%

95.4%

68.3

%SNLS3

BAO+WMAP7

With all systematics

0.0 0.1 0.2 0.3 0.4 0.5Ωm

−2.0

−1.5

−1.0

−0.5

w 99.7%

95.4%

SNLS3

BAO+WMAP7

Statistical only

0.0 0.1 0.2 0.3 0.4 0.5Ωm

−2.0

−1.5

−1.0

−0.5

w 99.7%

95.4%

SNLS3

BAO+WMAP7

With systematicsexcl. "calibration"

0.0 0.1 0.2 0.3 0.4 0.5Ωm

−2.0

−1.5

−1.0

−0.5

w

SNLS3

BAO+WMAP7

With systematics,Fixing α, β

Figure 2. Confidence contours in the cosmological parameters Ωm and w arising from fits to the combined SN Ia sample using the marginalization fitting approach,illustrating various systematic effects in the cosmological fits. In all panels, the SNLS3 SN Ia contours are shown in blue and combined BAO/WMAP7 constraints(Percival et al. 2010; Komatsu et al. 2011) in green. The combined constraints are shown in gray. The contours enclose 68.3%, 95.4%, and 99.7% of the probability,and the horizontal line shows the value of the cosmological constant, w = −1. Upper left: the baseline fit, where the SNLS3 contours include statistical and allidentified systematic uncertainties. Upper right: the filled SNLS3 contours include statistical uncertainties only; the dotted open contours refer to the baseline fit withall systematics included. Lower left: the filled SNLS3 contours exclude the SN Ia systematic uncertainties related to calibration. Lower right: the filled SNLS3 contoursresult from fixing α and β in the cosmological fits. See Tables 2 and 3 for numerical data.(A color version of this figure is available in the online journal.)

We then present our main cosmological results. We investi-gate a non-flat, w = −1 cosmology (fitting for Ωm and ΩΛ),a flat, constant w cosmology (fitting for Ωm and w), a non-flat cosmology with w free (fitting for w, Ωm, and Ωk), and acosmology where w(a) is allowed to vary via a simple linearparameterization w(a) = w0 + wa(1 − a) ≡ w0 + waz/(1 + z)(e.g., Chevallier & Polarski 2001; Linder 2003), fitting for Ωm,w0, and wa . We always fit for α, β, and MB .

The confidence contours for Ωm and w in a flat universecan be found in Figure 2 (upper left panel) for fits consideringall systematic and statistical uncertainties. Figure 2 also showsthe statistical-uncertainty-only cosmological fits in the upperright panel. The best-fitting cosmological parameters and thenuisance parameters α, β, M1

B , and M2B , for convenience

converted to MB assuming H0 = 70 km s−1 Mpc−1 (in thegrid marginalization approach, H0 is not fit for as it is perfectlydegenerate with MB), are in Table 1 (for non-flat, w = −1 fits)and Table 2 (for flat, constant w fits). We also list the parametersobtained with the χ2 minimization approach for comparison. Allthe fits, with and without the inclusion of systematic errors, are

consistent with a w = −1 universe: we find w = −1.043+0.054−0.055

(stat) and w = −1.068+0.080−0.082 (stat+sys). For comparison, with

no external constraints (i.e., SNLS3-only) the equivalent valuesare w = −0.90+0.16

−0.20 (stat) and w = −0.91+0.17−0.24 (stat+sys) (C11).

The lower right panel of Figure 2 shows the importance ofallowing the nuisance parameters α and β to vary in the fits,rather than holding them fixed at their best-fit values. Thisleads to not only smaller contours and hence underestimatedparameter uncertainties, but also a significant bias in the best-fit parameters (Table 3). Holding α and β fixed gives w =−1.117+0.081

−0.082, a ∼0.6σ shift in the value of w compared to thecorrect fit.

The residuals from the best-fitting cosmology as a functionof stretch and color can be found in Figure 3. No significantremaining trends between stretch and Hubble residual areapparent, but there is some evidence of a small trend betweenSN Ia color and luminosity at C < 0.15 (indicating that theseSNe prefer a smaller β, or a shallower slope, than the globalvalue). We examine this, and related issues, in more detail inSection 5.

7

Constraints on w (with Systematics)

Sullivan et al. 2011w = −1.061 ± 0.069 (stat + sys)

– 41 –

Table 3. Detailed summary of systematic uncertainties

Source Ωm w Relative areaa

Statistical only 0.2763+0.0163−0.0132 −1.0430+0.0543

−0.0546 1.0

All systematics 0.2736+0.0186−0.0145 −1.0676+0.0799

−0.0821 1.693

All systematics, except calibration 0.2756+0.0164−0.0133 −1.0481+0.0573

−0.0580 1.068

All systematics, except host term 0.2738+0.0186−0.0145 −1.0644+0.0790

−0.0809 1.677

All systematics, fixing α, βb 0.2656+0.0179−0.0144 −1.1168+0.0807

−0.0824 1.641

Contribution of different systematics:

Calibration 0.2750+0.0185−0.0150 −1.0581+0.0774

−0.0791 1.614

SN Ia model 0.2767+0.0163−0.0132 −1.0403+0.0543

−0.0547 1.013


−0.0548 1.002

Malmquist bias 0.2758+0.0163−0.0132 −1.0474+0.0548

−0.0553 1.014

Non SN Ia contamination 0.2763+0.0163−0.0132 −1.0430+0.0543

−0.0546 1.000

Milky Way extinction 0.2762+0.0164−0.0133 −1.0441+0.0553

−0.0557 1.023

SN redshift evolution 0.2763+0.0163−0.0132 −1.0408+0.0544

−0.0547 1.017

Host galaxy term 0.2762+0.0163−0.0132 −1.0453+0.0556

−0.0562 1.029

Calibration:

Colors of BD 17 4708 0.2719+0.0170−0.0137 −1.0720+0.0639

−0.0639 1.239

SED of BD 17 4708 0.2771+0.0170−0.0138 −1.0390+0.0623

−0.0630 1.205

SNLS zeropoints 0.2767+0.0168−0.0136 −1.0421+0.0603

−0.0609 1.166

Low-z zeropoints 0.2753+0.0164−0.0133 −1.0527+0.0578

−0.0586 1.078

SDSS zeropoints 0.2767+0.0164−0.0133 −1.0411+0.0544

−0.0548 1.015

SNLS filters 0.2789+0.0170−0.0138 −1.0330+0.0585

−0.0586 1.136

Lowz filters 0.2766+0.0163−0.0132 −1.0402+0.0547

−0.0550 1.010

SDSS filters 0.2770+0.0164−0.0133 −1.0396+0.0544

−0.0548 1.007

HST zeropoints 0.2769+0.0164−0.0133 −1.0412+0.0544

−0.0548 1.007

NICMOS nonlinearity 0.2767+0.0164−0.0133 −1.0418+0.0545

−0.0548 1.009

SN Ia model (light curve fitter):

SALT2 vs. SiFTO 0.2767+0.0163−0.0132 −1.0404+0.0543

−0.0547 1.012

Color uncert. model 0.2763+0.0163−0.0132 −1.0430+0.0543

−0.0546 1.001

SN Ia redshift evolution:

α 0.2763+0.0163−0.0132 −1.0430+0.0543

−0.0546 1.000

Systematic Error Budget

– 41 –




−0.0546 1.0

All systematics 0.2736+0.0186−0.0145 −1.0676+0.0799

−0.0821 1.693


−0.0580 1.068


−0.0809 1.677


−0.0824 1.641


Calibration 0.2750+0.0185−0.0150 −1.0581+0.0774

−0.0791 1.614

SN Ia model 0.2767+0.0163−0.0132 −1.0403+0.0543

−0.0547 1.013


−0.0548 1.002

Malmquist bias 0.2758+0.0163−0.0132 −1.0474+0.0548

−0.0553 1.014


−0.0546 1.000


−0.0557 1.023


−0.0547 1.017

Host galaxy term 0.2762+0.0163−0.0132 −1.0453+0.0556

−0.0562 1.029

Calibration:

Colors of BD 17 4708 0.2719+0.0170−0.0137 −1.0720+0.0639

−0.0639 1.239

SED of BD 17 4708 0.2771+0.0170−0.0138 −1.0390+0.0623

−0.0630 1.205

SNLS zeropoints 0.2767+0.0168−0.0136 −1.0421+0.0603

−0.0609 1.166

Low-z zeropoints 0.2753+0.0164−0.0133 −1.0527+0.0578

−0.0586 1.078

SDSS zeropoints 0.2767+0.0164−0.0133 −1.0411+0.0544

−0.0548 1.015

SNLS filters 0.2789+0.0170−0.0138 −1.0330+0.0585

−0.0586 1.136

Lowz filters 0.2766+0.0163−0.0132 −1.0402+0.0547

−0.0550 1.010

SDSS filters 0.2770+0.0164−0.0133 −1.0396+0.0544

−0.0548 1.007

HST zeropoints 0.2769+0.0164−0.0133 −1.0412+0.0544

−0.0548 1.007


−0.0548 1.009


SALT2 vs. SiFTO 0.2767+0.0163−0.0132 −1.0404+0.0543

−0.0547 1.012


−0.0546 1.001


α 0.2763+0.0163−0.0132 −1.0430+0.0543

−0.0546 1.000

– 41 –




−0.0546 1.0

All systematics 0.2736+0.0186−0.0145 −1.0676+0.0799

−0.0821 1.693


−0.0580 1.068


−0.0809 1.677


−0.0824 1.641


Calibration 0.2750+0.0185−0.0150 −1.0581+0.0774

−0.0791 1.614

SN Ia model 0.2767+0.0163−0.0132 −1.0403+0.0543

−0.0547 1.013


−0.0548 1.002

Malmquist bias 0.2758+0.0163−0.0132 −1.0474+0.0548

−0.0553 1.014


−0.0546 1.000


−0.0557 1.023


−0.0547 1.017

Host galaxy term 0.2762+0.0163−0.0132 −1.0453+0.0556

−0.0562 1.029

Calibration:

Colors of BD 17 4708 0.2719+0.0170−0.0137 −1.0720+0.0639

−0.0639 1.239

SED of BD 17 4708 0.2771+0.0170−0.0138 −1.0390+0.0623

−0.0630 1.205

SNLS zeropoints 0.2767+0.0168−0.0136 −1.0421+0.0603

−0.0609 1.166

Low-z zeropoints 0.2753+0.0164−0.0133 −1.0527+0.0578

−0.0586 1.078

SDSS zeropoints 0.2767+0.0164−0.0133 −1.0411+0.0544

−0.0548 1.015

SNLS filters 0.2789+0.0170−0.0138 −1.0330+0.0585

−0.0586 1.136

Lowz filters 0.2766+0.0163−0.0132 −1.0402+0.0547

−0.0550 1.010

SDSS filters 0.2770+0.0164−0.0133 −1.0396+0.0544

−0.0548 1.007

HST zeropoints 0.2769+0.0164−0.0133 −1.0412+0.0544

−0.0548 1.007


−0.0548 1.009


SALT2 vs. SiFTO 0.2767+0.0163−0.0132 −1.0404+0.0543

−0.0547 1.012


−0.0546 1.001


α 0.2763+0.0163−0.0132 −1.0430+0.0543

−0.0546 1.000

Calibration Errors

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7Redshift

0

5

10

15

20

25N

umbe

r175 SpectroscopicallyConfirmed PS1 SN Ia

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

PS1 SN Ia Redshift Histogram

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7Redshift

0

5

10

15

20

25N

umbe

r117 Spectroscopically

Confirmed and Fit PS1 SN Ia

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

PS1 SN Ia Redshift Histogram

PS1MD NewArmin8ce SN 000236 z=0.195 gri

0

200

400

600

800

g

c = -0.048 ± 0.014 x1 = -0.343 ± 0.154x0 x 104 = 1.341 ± 0.023 !2/dof = 18.2/33

0

0.5

1

1.5

2

!2diag/N = 6.4/11

0

250

500

750

r0

0.5

1

1.5

!2diag/N = 4.8/11

0

200

400

600

800

-25 0 25 50 75

i

Tobs " 55211

Flux

0

1

2

-25 0 25 50 75

!2diag/N = 7.1/15

Tobs " 55211

!2 per

Epo

ch

0.195

PS1MD NewArmin8ce SN 000174 z=0.244 griz

0

100

200

300

g

c = 0.063 ± 0.023 x1 = -0.294 ± 0.271x0 x 104 = 0.516 ± 0.015 !2/dof = 39.6/47

0

0.5

1

1.5

2!2diag/N = 7.6/15

0

100

200

300

r0

0.5

1

1.5

!2diag/N = 3.9/13

0

100

200

300

i0

5

10!2diag/N = 23.1/14

0

100

200

300

-25 0 25 50 75

z

Tobs " 55216.8

Flux

0

0.5

1

1.5

-25 0 25 50 75

!2diag/N = 4.9/9

Tobs " 55216.8

!2 per

Epo

ch

0.244

0.45


0

50

100

g

c = -0.144 ± 0.028 x1 = 0.526 ± 0.419x0 x 104 = 0.25 ± 0.008 !2/dof = 48.2/37

0

1

2

3

4!2diag/N = 17.3/12

0

100

200

r0

1

2

3

4!2diag/N = 13.7/12

0

100

200

i0

2

4!2diag/N = 9.7/9

0

50

100

150

-25 0 25 50 75

z

Tobs " 55570.7

Flux

0

1

2

3

-25 0 25 50 75

!2diag/N = 7.5/8

Tobs " 55570.7

!2 per

Epo

ch


0

20

40

g

c = -0.165 ± 0.082 x1 = 0.562 ± 1.573x0 x 104 = 0.105 ± 0.012 !2/dof = 35.9/56

0

5

10!2diag/N = 23.6/15

0

50

100

r0

1

2

3

!2diag/N = 6.1/14

0

25

50

75

i0

0.2

0.4

0.6!2diag/N = 2.6/15

0

50

100

-25 0 25 50 75

z

Tobs " 55468.2

Flux

0

0.5

1

1.5

-25 0 25 50 75

!2diag/N = 3.6/16

Tobs " 55468.2

!2 per

Epo

ch

0.635


0

500

1000

1500

g

c = 0.34 ± 0.037 x1 = -0.896 ± 0.267x0 x 104 = 3.703 ± 0.171 !2/dof = 30.8/6

0

2

4

6

8

!2diag/N = 13.1/3

0

1000

2000

3000

r0

2.5

5

7.5

10

!2diag/N = 13.1/4

0

1000

2000

3000

-25 0 25 50 75

i

Tobs " 55261.4

Flux

0

1

2

3

-25 0 25 50 75

!2diag/N = 4.0/3

Tobs " 55261.4

!2 per

Epo

ch

0.081

0.14


0

500

1000

g

c = 0.032 ± 0.031 x1 = 2.343 ± 0.261x0 x 104 = 1.663 ± 0.049 !2/dof = 242.5/20

0

20

40 !2diag/N = 127.3/8

0

500

1000

r0

10

20

30

!2diag/N = 77.8/8

0

500

1000

-25 0 25 50 75

i

Tobs " 55500.2

Flux

0

5

10

15

-25 0 25 50 75

!2diag/N = 37.4/8

Tobs " 55500.2

!2 per

Epo

ch

0.101


0

1000

2000

g

c = 0.108 ± 0.033 x1 = 3.58 ± 0.295x0 x 104 = 3.272 ± 0.11 !2/dof = 313.5/27

0

20

40

60

80

!2diag/N = 148.9/10

0

1000

2000

r0

10

20

30!2diag/N = 95.9/10

0

1000

2000

-25 0 25 50 75

i

Tobs " 55649.6

Flux

0

10

20

30

-25 0 25 50 75

!2diag/N = 68.7/11

Tobs " 55649.6

!2 per

Epo

ch

0.105


0

500

1000

1500

g

c = 0.007 ± 0.056 x1 = -1.351 ± 0.505x0 x 104 = 2.762 ± 0.163 !2/dof = 9.8/7

0

2.5

5

7.5

10

!2diag/N = 8.9/4

0

500

1000

1500

r0

0.02

0.04

0.06

!2diag/N = 0.2/4

0

500

1000

1500

-25 0 25 50 75

i

Tobs " 55547.7

Flux

0

0.1

0.2

0.3

-25 0 25 50 75

!2diag/N = 0.4/3

Tobs " 55547.7

!2 per

Epo

ch


0

20

40

60

g

c = 0.027 ± 0.095 x1 = 2.84 ± 2.657x0 x 104 = 0.113 ± 0.012 !2/dof = 8.5/14

0

0.2

0.4

0.6

0.8

!2diag/N = 0.8/4

0

25

50

75

r0

0.1

0.2

0.3 !2diag/N = 0.6/4

0

25

50

75

i0

0.25

0.5

0.75

1!2diag/N = 3.0/5

0

50

100

-25 0 25 50 75

z

Tobs " 55368.5

Flux

0

0.5

1

1.5

-25 0 25 50 75

!2diag/N = 2.9/5

Tobs " 55368.5

!2 per

Epo

ch


0

200

400

600

g

c = -0.153 ± 0.028 x1 = 0.686 ± 0.493x0 x 104 = 1.021 ± 0.041 !2/dof = 8.1/11

0

0.2

0.4 !2diag/N = 0.9/4

0

200

400

600

r0

0.5

1

1.5

2!2diag/N = 2.0/4

0

200

400

600

i0

0.5

1

1.5

!2diag/N = 2.6/4

0

200

400

-25 0 25 50 75

z

Tobs " 55583.4

Flux

0

0.5

1

1.5

2

-25 0 25 50 75

!2diag/N = 2.5/3

Tobs " 55583.4

!2 per

Epo

ch


0

25

50

75

100

g

c = -0.12 ± 0.044 x1 = 0.776 ± 0.647x0 x 104 = 0.219 ± 0.012 !2/dof = 46.8/37

0

1

2

3!2diag/N = 8.4/9

0

100

200

r0

2

4

6

8

!2diag/N = 12.6/11

0

50

100

150

i0

1

2

3

4

!2diag/N = 7.3/8

0

50

100

-25 0 25 50 75

z

Tobs " 55324.5

Flux

0

2

4

6

-25 0 25 50 75

!2diag/N = 17.7/13

Tobs " 55324.5

!2 per

Epo

ch


0

200

400

600

800

g

c = 0.081 ± 0.032 x1 = -0.748 ± 0.378x0 x 104 = 1.333 ± 0.053 !2/dof = 18/13

0

1

2

3

4!2diag/N = 11.3/9

0

250

500

750

r0

1

2

3

4

!2diag/N = 6.7/8

0

250

500

750

-25 0 25 50 75

i

Tobs " 55586.2

Flux

-1

-0.5

0

0.5

1

-25 0 25 50 75

!2diag/N = 0.0/0

Tobs " 55586.2

!2 per

Epo

ch

PS1 Hubble Diagram

38

40

42

44

46m

-M SALT

M =0.3, !"#$M =0.3, !"#"M=1.0, !"#"

0.0 0.2 0.4 0.6 0.8z

-1.0

-0.5

0.0

0.5

(m-M

)

PS1-Only Hubble Diagram (117 SNe)

0.0 0.5 1.0 1.5M

0.0

0.5

1.0

1.5PS1_Hubble2

PS1_Hubble2

PS1-Only Banana Plot

0.0 0.5 1.0 1.5 2.0 2.5!M

-1

0

1

2

3

!"

68.3%

95.4%

95.4%

99.7%

99.7

%

99.7%

No Big

Bang

!tot =1

Expands to Infinity

Recollapses !"=0Open

Closed

Accelerating

Decelerating

q0=0

q0=-0.5

q0=0.5

^

MLCS

0.0 0.5 1.0 1.5 2.0 2.5!M

-1

0

1

2

3

!"

68.3%

95.4%

95.4%

99.7%

99.7%

99.7%

No Big

Bang

!tot =1

Expands to Infinity


Closed

Accelerating

Decelerating

q0=0

q0=-0.5

q0=0.5

^

#m15(B)

No. 3, 1998 EVIDENCE FOR AN ACCELERATING UNIVERSE 1023

FIG. 6.ÈJoint conÐdence intervals for from SNe Ia. The solid()M

, )")contours are results from the MLCS method applied to well-observed SNeIa light curves together with the snapshot method et al.(Riess 1998b)applied to incomplete SNe Ia light curves. The dotted contours are for thesame objects excluding the unclassiÐed SN 1997ck (z \ 0.97). Regions rep-resenting speciÐc cosmological scenarios are illustrated. Contours areclosed by their intersection with the line )

M\ 0.

The normalized PDF comes from dividing this relativePDF by its sum over all possible states,

p(H0, )m, )" o l0)

\ exp ([s2/2)/~== dH0 /~== d)" /0= exp ([s2/2)d)

M, (10)

neglecting the unphysical regions. The most likely values forthe cosmological parameters and preferred regions ofparameter space are located where is mini-equation (4)mized or, alternately, is maximized.equation (10)

The Hubble constants as derived from the MLCSmethod, 65.2 ^ 1.3 km s~1 Mpc~1, and from the template-Ðtting approach, 63.8 ^ 1.3 km s~1 Mpc~1, are extremelyrobust and attest to the consistency of the methods. Thesedeterminations include only the statistical component oferror resulting from the point-to-point variance of the mea-sured Hubble Ñow and do not include any uncertainty inthe absolute magnitude of SN Ia. From three photoelec-trically observed SNe Ia, SN 1972E, SN 1981B, and SN1990N (Saha et al. the SN Ia absolute magni-1994, 1997),tude was calibrated from observations of Cepheids in thehost galaxies. The calibration of the SN Ia magnitude fromonly three objects adds an additional 5% uncertainty to theHubble constant, independent of the uncertainty in the zeropoint of the distance scale. The uncertainty in the Cepheid

distance scale adds an uncertainty of D10% to the derivedHubble constant & Walker(Feast 1987 ; Kochanek 1997 ;

& Freedman A realistic determination of theMadore 1998).Hubble constant from SNe Ia would give 65 ^ 7 km s~1Mpc~1, with the uncertainty dominated by the systematicuncertainties in the calibration of the SN Ia absolute magni-tude. These determinations of the Hubble constant employthe Cepheid distance scale of & FreedmanMadore (1991),which uses a distance modulus to the Large MagellanicCloud (LMC) of 18.50 mag. Parallax measurements by theHipparcos satellite indicate that the LMC distance could begreater, and hence our inferred Hubble constant smaller, by5% to 10% though not all agree with the inter-(Reid 1997),pretation of these parallaxes & Freedman(Madore 1998).All subsequent indications in this paper for the cosmo-logical parameters and are independent of the value)

M)"for the Hubble constant or the calibration of the SN Ia

absolute magnitude.Indications for and independent from can be)

M)", H0,

found by reducing our three-dimensional PDF to twodimensions. A joint conÐdence region for and is)

M)"derived from our three-dimensional likelihood space

p()M

, )" o l0) \P~=

=p()

M, )", H0 o l0)dH0 . (11)


, )")contours are results from the template-Ðtting method applied to well-observed SNe Ia light curves together with the snapshot method et(Riessal. applied to incomplete SNe Ia light curves. The dotted contours1998b)are for the same objects excluding the unclassiÐed SN 1997ck (z \ 0.97).Regions representing speciÐc cosmological scenarios are illustrated. Con-tours are closed by their intersection with the line )

M\ 0.

Riess et al. 1998

A Humble Comparison

0.0 0.5 1.0 1.5 2.0 2.5!M

-1

0

1

2

3

!"

68.3%

95.4%

95.4%

99.7%

99.7

%

99.7%

No Big

Bang

!tot =1

Expands to Infinity


Closed

Accelerating

Decelerating

q0=0

q0=-0.5

q0=0.5

^

MLCS

0.0 0.5 1.0 1.5 2.0 2.5!M

-1

0

1

2

3

!"

68.3%

95.4%

95.4%

99.7%

99.7%

99.7%

No Big

Bang

!tot =1

Expands to Infinity


Closed

Accelerating

Decelerating

q0=0

q0=-0.5

q0=0.5

^

#m15(B)

No. 3, 1998 EVIDENCE FOR AN ACCELERATING UNIVERSE 1023


, )")contours are results from the MLCS method applied to well-observed SNeIa light curves together with the snapshot method et al.(Riess 1998b)applied to incomplete SNe Ia light curves. The dotted contours are for thesame objects excluding the unclassiÐed SN 1997ck (z \ 0.97). Regions rep-resenting speciÐc cosmological scenarios are illustrated. Contours areclosed by their intersection with the line )

M\ 0.

The normalized PDF comes from dividing this relativePDF by its sum over all possible states,

p(H0, )m, )" o l0)

\ exp ([s2/2)/~== dH0 /~== d)" /0= exp ([s2/2)d)

M, (10)

neglecting the unphysical regions. The most likely values forthe cosmological parameters and preferred regions ofparameter space are located where is mini-equation (4)mized or, alternately, is maximized.equation (10)

The Hubble constants as derived from the MLCSmethod, 65.2 ^ 1.3 km s~1 Mpc~1, and from the template-Ðtting approach, 63.8 ^ 1.3 km s~1 Mpc~1, are extremelyrobust and attest to the consistency of the methods. Thesedeterminations include only the statistical component oferror resulting from the point-to-point variance of the mea-sured Hubble Ñow and do not include any uncertainty inthe absolute magnitude of SN Ia. From three photoelec-trically observed SNe Ia, SN 1972E, SN 1981B, and SN1990N (Saha et al. the SN Ia absolute magni-1994, 1997),tude was calibrated from observations of Cepheids in thehost galaxies. The calibration of the SN Ia magnitude fromonly three objects adds an additional 5% uncertainty to theHubble constant, independent of the uncertainty in the zeropoint of the distance scale. The uncertainty in the Cepheid

distance scale adds an uncertainty of D10% to the derivedHubble constant & Walker(Feast 1987 ; Kochanek 1997 ;

& Freedman A realistic determination of theMadore 1998).Hubble constant from SNe Ia would give 65 ^ 7 km s~1Mpc~1, with the uncertainty dominated by the systematicuncertainties in the calibration of the SN Ia absolute magni-tude. These determinations of the Hubble constant employthe Cepheid distance scale of & FreedmanMadore (1991),which uses a distance modulus to the Large MagellanicCloud (LMC) of 18.50 mag. Parallax measurements by theHipparcos satellite indicate that the LMC distance could begreater, and hence our inferred Hubble constant smaller, by5% to 10% though not all agree with the inter-(Reid 1997),pretation of these parallaxes & Freedman(Madore 1998).All subsequent indications in this paper for the cosmo-logical parameters and are independent of the value)

M)"for the Hubble constant or the calibration of the SN Ia

absolute magnitude.Indications for and independent from can be)

M)", H0,

found by reducing our three-dimensional PDF to twodimensions. A joint conÐdence region for and is)

M)"derived from our three-dimensional likelihood space

p()M

, )" o l0) \P~=

=p()

M, )", H0 o l0)dH0 . (11)


, )")contours are results from the template-Ðtting method applied to well-observed SNe Ia light curves together with the snapshot method et(Riessal. applied to incomplete SNe Ia light curves. The dotted contours1998b)are for the same objects excluding the unclassiÐed SN 1997ck (z \ 0.97).Regions representing speciÐc cosmological scenarios are illustrated. Con-tours are closed by their intersection with the line )

M\ 0.

0.0 0.5 1.0 1.5M

0.0

0.5

1.0

1.5PS1_Hubble2

PS1_Hubble2

Riess et al. 1998

A Humble Comparison




Stat only 0.19+0.08−0.10 −0.90+0.16

−0.20 1 −1.031 ± 0.058

All systematics 0.18 ± 0.10 −0.91+0.17−0.24 1.85 −1.08+0.10

−0.11 Section 4.4

Calibration 0.191+0.095−0.104 −0.92+0.17

−0.23 1.79 −1.06 ± 0.10 Section 5.1

SN model 0.195+0.086−0.101 −0.90+0.16

−0.20 1.02 −1.027 ± 0.059 Section 5.2


−0.20 1.03 −1.034 ± 0.059 Section 5.3

Malmquist bias 0.198+0.084−0.100 −0.91+0.16

−0.20 1.07 −1.037 ± 0.060 Section 5.4


−0.20 1 −1.031 ± 0.058 Section 5.5


−0.20 1.05 −1.032 ± 0.060 Section 5.6

SN evolution 0.185+0.088−0.099 −0.88+0.15

−0.20 1.02 −1.028 ± 0.059 Section 5.7

Host relation 0.198+0.085−0.102 −0.91+0.16

−0.21 1.08 −1.034 ± 0.061 Section 5.8


0.0 0.3 0.6 0.9 1.2 1.5z

−0.01

0.00

0.01

∆ m

B

0.0 0.3 0.6 0.9 1.2 1.5z

−0.01

0.00

0.01

∆ C

−0.01

0.00

0.01

∆ s

−0.05

0.00

0.05

∆ m

corr



0.0 0.2 0.4 0.6 0.8 1.0Ωm

0.0

0.5

1.0

1.5

ΩΛ

99.7%

99.7%

99.7%

95.4%

95.4%

68.3%

Accelerating

Decelerating

No big bang








14

PS1 Still Has Work to Do

Conley et al. 2011




Stat only 0.19+0.08−0.10 −0.90+0.16

−0.20 1 −1.031 ± 0.058

All systematics 0.18 ± 0.10 −0.91+0.17−0.24 1.85 −1.08+0.10

−0.11 Section 4.4

Calibration 0.191+0.095−0.104 −0.92+0.17

−0.23 1.79 −1.06 ± 0.10 Section 5.1

SN model 0.195+0.086−0.101 −0.90+0.16

−0.20 1.02 −1.027 ± 0.059 Section 5.2


−0.20 1.03 −1.034 ± 0.059 Section 5.3

Malmquist bias 0.198+0.084−0.100 −0.91+0.16

−0.20 1.07 −1.037 ± 0.060 Section 5.4


−0.20 1 −1.031 ± 0.058 Section 5.5


−0.20 1.05 −1.032 ± 0.060 Section 5.6

SN evolution 0.185+0.088−0.099 −0.88+0.15

−0.20 1.02 −1.028 ± 0.059 Section 5.7

Host relation 0.198+0.085−0.102 −0.91+0.16

−0.21 1.08 −1.034 ± 0.061 Section 5.8


0.0 0.3 0.6 0.9 1.2 1.5z

−0.01

0.00

0.01

∆ m

B

0.0 0.3 0.6 0.9 1.2 1.5z

−0.01

0.00

0.01

∆ C

−0.01

0.00

0.01

∆ s

−0.05

0.00

0.05

∆ m

corr



0.0 0.2 0.4 0.6 0.8 1.0Ωm

0.0

0.5

1.0

1.5

ΩΛ

99.7%

99.7%

99.7%

95.4%

95.4%

68.3%

Accelerating

Decelerating

No big bang








14

PS1 Still Has Work to Do

Conley et al. 2011

0.0 0.5 1.0 1.5M

0.0

0.5

1.0

1.5PS1_Hubble2

PS1_Hubble2

The Future...

SurveyRedshift Range

SNe Today

SNe in 2015

Low-z 0 – 0.1 123 250

PTF 0 – 0.1 200 500

SDSS 0.1 – 0.4 93 400

SNLS 0.4 – 1 242 242?

DES 0.4 – 1 0 100 – 1000

HST 0.8 – 2 14 50

PS1 0 – 0.7 117 – 175 250 – 500

SN Ia host galaxies 13

7 8 9 10 11 12LOG host galaxy Mstellar (MO • )

-0.4

-0.2

0.0

0.2

0.4

mBco

rr - m

Bmod

(s, C

)

s!1s<1Mean residual

SNLS

0.0 0.2 0.4 0.6 0.8 1.0Relative number

High-MstellarLow-Mstellar

7 8 9 10 11 12LOG host galaxy Mstellar (MO • )

-0.4

-0.2

0.0

0.2

0.4

mBco

rr - m

Bmod

(s, C

)

Low redshift

0.0 0.2 0.4 0.6 0.8 1.0Relative number

Figure 4. As Fig.3, but for Mstellar instead of sSFR.

Z split High-Z hosts Low-Z hosts(12+log(O/H)) NSN α β MB r.m.s. NSN α β MB r.m.s.

8.70 102 1.512±0.147 3.238±0.158 -19.195±0.014 0.142 93 1.661±0.175 3.800±0.192 -19.115±0.018 0.1498.75 92 1.577±0.152 3.172±0.165 -19.204±0.015 0.143 103 1.688±0.161 3.848±0.176 -19.110±0.016 0.1468.80 81 1.601±0.155 3.102±0.170 -19.210±0.015 0.139 114 1.612±0.160 3.747±0.165 -19.124±0.015 0.1448.85 61 1.534±0.185 3.095±0.194 -19.217±0.018 0.139 134 1.739±0.148 3.614±0.151 -19.125±0.014 0.1438.90 34 1.526±0.187 2.795±0.225 -19.218±0.021 0.113 161 1.491±0.130 3.619±0.139 -19.151±0.012 0.148

Table 6. As Table 4, but for Z instead of sSFR.

by restricting our analysis to those SNe Ia lying at z < 0.85,away from the redshift limit of SNLS. The total Malmquistbias (including spectroscopic selection) on our SNe belowthis redshift is < 0.015mag (Perrett et al. 2010), comparedwith the size of the magnitude difference in our results of∼0.1mag. We have also tested for the existence of this ob-servational selection effect by examining the SN Ia residualsversus the percentage increase of the SN flux over its host.Below a percentage increase of 100% (i.e., the SN is as bright

as the host measured through a small aperture), identifica-tion becomes more difficult (e.g. Howell et al. 2005). Ourkey diagnostic would be to see brighter SNe (after correc-tion) when the percentage increase is <100%, and fainterSNe at percentage increases >100%, if this selection effectwere serious. We show these data in Figure 8. No effect ispresent in our data; only weak trends are present with thepercentage increase as expected given the weak correlationwith Mstellar.

c© 0000 RAS, MNRAS 000, 1–23

Sullivan et al. 2010

Host – Hubble Residual Relation

!0.2 !0.1 0.0 0.1 0.2Intrinsic Bmax!Vmax (mag)

!9

!10

!11

!12

!13

!14

!15

!16Si

II V

eloc

ity a

t Max

imum

(103 k

m s!

1 )Color – Velocity Relation

Foley, Sanders, & Kirshner 2011

Reduce gaps, increase time baseline

Better Calibration

Host-galaxy properties

MOS of SN Hosts

KP8 Wish List

Reduce gaps, increase time baseline

Better Calibration

Host-galaxy properties

MOS of SN Hosts

Better coordination MDS priority after gaps Single epoch before/after add/drop

Gene’s BD+17 observations

Galaxy photo-z server, KP9

Cross-KP coordination

KP8 Wish List

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