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EXPLORING SUPERNOVA SYSTEMATIC UNCERTAINTIES WITH THE PS1 SN IA SAMPLE Dan Scolnic1, Armin Rest2, Mark Huber4, Adam Riess1, Dillon Brout1, Edo Berger3,
Ryan Chornock3, Ryan Foley3, John Tonry4, PS1 Transients Team
1Johns
"
Hopkins University,2Space Telescope Science Institute, 3Harvard University, 4University of Hawaii
Abstract We probe the systemaAc uncertainAes from the 117 supernovae (SNe) in the Pan-­‐STARRS1 (PS1) Sample along with 209 SNe from combined low-­‐redshiS surveys. We find the largest systemaAc uncertainty is due to calibraAon, and we double the number of Calspec standards (13) used to determine the PS1 calibraAon system and analyze discrepancies with the SDSS-­‐II calibraAon system. We include here the first esAmates of host galaxy masses of PS1 SNe and find agreement with previously reported relaAons between host-­‐galaxy mass and SN absolute brightness at 1.6σ which we use to correct our light curve fits. We accurately model the PS1 supernova survey as well as the low-­‐z supernova surveys in order to determine the selecAon effects in these samples. We also explore systemaAc uncertainAes due to correlated velocity flows and the minimum redshiS used in the sample as well as possible evoluAonary effects in the light curve fit parameters. When we include systemaAc uncertainAes in our analysis of cosmological parameters, we derive Ωm =0.275±0.033(Stat)±0.013(Sys) and w =−0.923±0.093(Stat)±0.054(Sys). The PS1 survey takes advantage of the precise photometric system as measured by Tonry (2012) and propagated across the sky by Schlafly & Finkbeiner (2012). All of the most recent supernova surveys have error budgets dominated by calibraAon uncertainAes, so accurate photometric systems are of the highest priority. ObservaAons of Calspec Standards w
-0.84
-0.86
-0.88
-0.90
-0.92
-0.94
-0.96
-0.02 -0.01 0.00 0.01
z Cal (mag)
0.02 -0.02 -0.01 0.00 0.01
r Cal (mag)
0.02
-0.02 -0.01 0.00 0.01
i Cal (mag)
0.02
0.8
0.01
0.9
1.0
1.1
MW E(B-V) Scale
0.02
Min Z
1.2
0.8
0.03
0.9
1.0
1.1
Error Scale
1.2
9.6 9.8 10.0 10.2 10.4
log Host Gal Mass Split
-0.2
0.0
-0.4
-0.2 0.0
0.2
r-i (Mag)
0.4
The Pan-­‐STARRS AB magnitude system is based on ’tweaking’ highly accurate measurements of the PS1 system throughput and filter transmissions into agreement with observaAons of HST standard stars and star clusters. Tonry (2012) notes 0.02 mag discrepancies at 3-­‐4σ aSer color-­‐transforming the SDSS catalogs into the PS1 system using PS1 filter transmissions. We double the number of Calspec standards to define the photometric system and conclude that the PS1 and SDSS photometric systems agree within 1σ in each passband. Other
avg: -0.043+/-0.039 (14)
avg: -0.058+/-0.047 (9)
CSP
-1
-0.2
-2
-0.2
-2
0.4
avg: 0.019+/-0.019 (47)
avg: 0.000+/-0.016 (69)
CFA4
PS1
-2
0.1
-0.2
0.0
avg: -0.011+/-0.021 (46)
avg: -0.008+/-0.012 (120)
-0.6
0.00 0.02 0.04 0.06 0.08 0.00 0.02 0.04 0.06 0.08
z
z Ideally, an individual survey can be used to determine distances of SNe at both low redshiSs (z < 0.1) and medium/high redshiSs (z ∼ 0.5) so that one can bypass tension between various samples (shown above for low-­‐z samples). Here we include low-­‐z data from all samples with well measured calibraAon systems. 0
-0.2
0.0
CFA4
2
1
0
-0.1
-1
-0.2
-2
0.00
20
40
SNRMax
60
80
-2
0
x1
2
4
15
10
5
10
15
TGapMax
20
5
0
0
25
40
20
30
15
20
10
10
5
0
-4
0.2
2
0.1
1
0.0
0
-0.1
-1
-0.2
-2
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
Redshift
0.05
-0.00
-0.05
-0.10
-0.15
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
z
Low M -­‐ -­‐ Low
M_S
0.4
1
-1
0.2
80
High
M_S
High M -­‐ 2
-0.1
0.2
-0.4
CFA3
0.2
0.0
60
IV. Host Galaxy RelaAon 0
-1
-0.2
40
Ndof
25
20
To determine the correcAon for the selecAon bias towards towards brighter SNIa, we must accurately be able to simulate the PS Medium Deep Survey and the spectroscopic follow-­‐up. We apply the SNANA MC code (Kessler 2009) to generate realisAc SNIa light curves with the same cadence, weather condiAons, PSF characterisAcs and zeropoints as our actual data. 2
-0.1
0.1
20
1
0.0
0.0
-0.6
0.6
CSP
CFA3
0.2
-0.4
5
0
0
0
-0.1
x1
c
-0.2
0.4
0.0
0.1
0.0
-0.6
0.6
1
0.2
0.2
-0.4
0.1
x1
z
0.4
CFA2
c
0.2
-0.6
0.6
avg: -0.020+/-0.050 (8)
c
i
avg: -0.013+/-0.037 (16)
JRK072
x1
-0.4
10
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
Redshift
Hubble Residual (Mags)
c
0.0
0.2
x1
CFA1
0.2
µ -µ(Best) (mag)
PS1 Obs-Synthetic (Mag)
Calon
10
-0.3 -0.2 -0.1 0.0 0.1 0.2 0.3
c
VI. Other Samples 0.4
15
0
0.6
0.4
15
60
50
40
30
20
10
0
0
0.02
g
0.6
25
20
5
0
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
Redshift
-0.84
-0.86
-0.88
-0.90
-0.92
-0.94
-0.96
0.7 0.8 0.9 1.0 1.1 1.2 1.3
Malmquist Bias Scale
r
25
20
x1
II. CalibraAon UncertainAes -0.84
-0.86
-0.88
-0.90
-0.92
-0.94
-0.96
-0.02 -0.01 0.00 0.01
g Cal (mag)
c
w
w
The Pan-­‐STARRS1 (PS1) Medium Deep survey was designed to detect and observe thousands of SNIa in order to measure the equaAon of state of dark energy w. The PS1 supernova survey represents a new generaAon of s u p e r n o v a s u r v e y s i n w h i c h t h e fi n a l uncertainAes are dominated by systemaAc errors and it is no longer possible to spectroscopically idenAfy more than a small fracAon of the SNe candidates. It is now imperaAve to analyze a growing list of systemaAc uncertainAes and rely on highly accurate simulaAons of the supernova surveys in order to fully explore various selecAon effects. PS1
PS1-SDSS tweaked
III. SelecAon Effects V. Overall SystemaAc UncertainAes Selection Efficiency Bias (Mags)
I. Intro 0.02
0.04
0.06
0.08
z 0.00
0.02
0.04
0.06
0.08
For the low-­‐z sample, we simulate each survey. It is much more difficult because of the smaller sample sizes, discoveries that are external to the survey, and in some cases, mulAple telescopes used for observaAons. We correct for the selecAon bias by observing if there is a trend in the color and stretch distribuAon with redshiS (shown above, the curves are derived from our simulaAons). Poster based on: Dan Scolnic, Armin Rest, Mark Huber, Adam Riess, Steve Rodney, Edo Berger, Ryan Chornock, Ryan Foley, and John Tonry Probing SystemaAc UncertanAes of the PS1 SNIa Sample In PreparaAon (2013) Contact: [email protected] 0.2
0.0
-0.2
-0.4
7
8
9 10 11 12
Host Galaxy Mass
50
We correct for the the host-­‐galaxy Hubble relaAon as shown in Kelly (2007) and Sullivan (2010) for PS1. They find that the host-­‐galaxy masses are correlated with the distance residuals from the cosmological best fit where SNe are ∼ 0.075 mags brighter in massive host galaxies (>10^10 M⊙ ) than less massive galaxies.