SiFTO: An Empirical Method for Fitting SN Ia Light Curves

Conley, A.; Sullivan, M.; Hsiao, E. Y.; Guy, J.; Astier, P.; Balam, D.; Balland, C.; Basa, S.; Carlberg, R. G.; Fouchez, D.; Hardin, D.; Howell, D. A.; Hook, I. M.; Pain, R.; Perrett, K.; Pritchet, C. J.; Regnault, Nicolas

doi:10.1086/588518

Cited by 242 publications

(365 citation statements)

References 58 publications

(36 reference statements)

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“…The "combined" sample of Conley et al (2011) combines the results of two light-curve fitting codes, SiFTO (Conley et al 2008) and SALT2 (Guy et al 2007), to produce a peak apparent B-band magnitude, m B , stretch parameter s and colour C for each supernova. To explore the impact of light-curve fitting, we also analyse separately the SiFTO and SALT2 parameters.…”

Section: The Snls Compilationmentioning

confidence: 99%

Planck2013 results. XVI. Cosmological parameters

Ade¹,

Aghanim²,

Armitage-Caplan³

et al. 2014

A&A

5,001

163

2,253

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This paper presents the first cosmological results based on Planck measurements of the cosmic microwave background (CMB) temperature and lensing-potential power spectra. We find that the Planck spectra at high multipoles ( > ∼ 40) are extremely well described by the standard spatiallyflat six-parameter ΛCDM cosmology with a power-law spectrum of adiabatic scalar perturbations. Within the context of this cosmology, the Planck data determine the cosmological parameters to high precision: the angular size of the sound horizon at recombination, the physical densities of baryons and cold dark matter, and the scalar spectral index are estimated to be θ * = (1.04147 ± 0.00062) × 10 −2 , Ω b h 2 = 0.02205 ± 0.00028, Ω c h 2 = 0.1199 ± 0.0027, and n s = 0.9603 ± 0.0073, respectively (note that in this abstract we quote 68% errors on measured parameters and 95% upper limits on other parameters). For this cosmology, we find a low value of the Hubble constant, H 0 = (67.3 ± 1.2) km s −1 Mpc −1 , and a high value of the matter density parameter, Ω m = 0.315 ± 0.017. These values are in tension with recent direct measurements of H 0 and the magnituderedshift relation for Type Ia supernovae, but are in excellent agreement with geometrical constraints from baryon acoustic oscillation (BAO) surveys. Including curvature, we find that the Universe is consistent with spatial flatness to percent level precision using Planck CMB data alone. We use high-resolution CMB data together with Planck to provide greater control on extragalactic foreground components in an investigation of extensions to the six-parameter ΛCDM model. We present selected results from a large grid of cosmological models, using a range of additional astrophysical data sets in addition to Planck and high-resolution CMB data. None of these models are favoured over the standard six-parameter ΛCDM cosmology. The deviation of the scalar spectral index from unity is insensitive to the addition of tensor modes and to changes in the matter content of the Universe. We find an upper limit of r 0.002 < 0.11 on the tensor-to-scalar ratio. There is no evidence for additional neutrino-like relativistic particles beyond the three families of neutrinos in the standard model. Using BAO and CMB data, we find N eff = 3.30 ± 0.27 for the effective number of relativistic degrees of freedom, and an upper limit of 0.23 eV for the sum of neutrino masses. Our results are in excellent agreement with big bang nucleosynthesis and the standard value of N eff = 3.046. We find no evidence for dynamical dark energy; using BAO and CMB data, the dark energy equation of state parameter is constrained to be w = −1.13 +0.13 −0.10 . We also use the Planck data to set limits on a possible variation of the fine-structure constant, dark matter annihilation and primordial magnetic fields. Despite the success of the six-parameter ΛCDM model in describing the Planck data at high multipoles, we note that this cosmology does not provide a good fit to the temperature power spectrum at low multipoles. T...

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Section: The Snls Compilationmentioning

confidence: 99%

Planck2013 results. XVI. Cosmological parameters

Ade¹,

Aghanim²,

Armitage-Caplan³

et al. 2014

A&A

5,001

163

2,253

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“…In current implementations, MLCS fitters are "trained" on local supernovae to determine the relationships between multi-band light curve shapes and peak absolute magnitudes, and these relationships are applied to distant supernovae to measure D L (z). SALT-style fitters (which include the SiFTO [Conley et al 2008] algorithm applied to SNLS3) instead apply a global, simultaneous fit of parameters describing cosmology and the relationship between supernova light curves and absolute magnitude. Of greater practical import, however, is the different treatment of supernova colors in the two methods.…”

Section: Figurementioning

confidence: 99%

Observational probes of cosmic acceleration

et al. 2013

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The accelerating expansion of the universe is the most surprising cosmological discovery in many decades, implying that the universe is dominated by some form of "dark energy" with exotic physical properties, or that Einstein's theory of gravity breaks down on cosmological scales. The profound implications of cosmic acceleration have inspired ambitious efforts to understand its origin, with experiments that aim to measure the history of expansion and growth of structure with percent-level precision or higher. We review in detail the four most well established methods for making such measurements: Type Ia supernovae, baryon acoustic oscillations (BAO), weak gravitational lensing, and the abundance of galaxy clusters. We pay particular attention to the systematic uncertainties in these techniques and to strategies for controlling them at the level needed to exploit "Stage IV" dark energy facilities such as BigBOSS, LSST, Euclid, and WFIRST. We briefly review a number of other approaches including redshift-space distortions, the Alcock-Paczynski effect, and direct measurements of the Hubble constant H 0 . We present extensive forecasts for constraints on the dark energy equation of state and parameterized deviations from General Relativity, achievable with Stage III and Stage IV experimental programs that incorporate supernovae, BAO, weak lensing, and cosmic microwave background data. We also show the level of precision required for clusters or other methods to provide constraints competitive with those of these fiducial programs. We emphasize the value of a balanced program that employs several of the most powerful methods in combination, both to cross-check systematic uncertainties and to take advantage of complementary information. Surveys to probe cosmic acceleration produce data sets that support a wide range of scientific investigations, and they continue the longstanding astronomical tradition of mapping the universe in ever greater detail over ever larger scales.

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“…The distance to each object classified as an SN Ia is then determined from the multi-color time series photometry using one or more light-curve fitting models, e.g., SALT2 (Guy et al 2007), MLCS2k2 (Riess et al 1996;Jha et al 2007), and SiFTO (Conley et al 2008). Methods for constraining the absolute magnitude of an observed SN based on spectroscopic line ratios have also been developed and applied to nearby SNe (Foley et al 2008;Bailey et al 2009;Chotard et al 2011;Nordin et al 2011;Blondin et al 2012;Silverman et al 2012), though as of yet they have not been tested over a cosmologically interesting redshift range.…”

Section: Introductionmentioning

confidence: 99%

COSMOLOGY WITH PHOTOMETRICALLY CLASSIFIED TYPE Ia SUPERNOVAE FROM THE SDSS-II SUPERNOVA SURVEY

Campbell

D’Andrea

Nichol

et al. 2013

ApJ

112

128

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We present the cosmological analysis of 752 photometrically classified Type Ia Supernovae (SNe Ia) obtained from the full Sloan Digital Sky Survey II (SDSS-II) Supernova (SN) Survey, supplemented with host-galaxy spectroscopy from the SDSS-III Baryon Oscillation Spectroscopic Survey. Our photometric-classification method is based on the SN classification technique of Sako et al., aided by host-galaxy redshifts (0.05 < z < 0.55). SuperNova ANAlysis simulations of our methodology estimate that we have an SN Ia classification efficiency of 70.8%, with only 3.9% contamination from core-collapse (non-Ia) SNe. We demonstrate that this level of contamination has no effect on our cosmological constraints. We quantify and correct for our selection effects (e.g., Malmquist bias) using simulations. When fitting to a flat ΛCDM cosmological model, we find that our photometric sample alone gives Ω m = 0.24 +0.07 −0.05 (statistical errors only). If we relax the constraint on flatness, then our sample provides competitive joint statistical constraints on Ω m and Ω Λ , comparable to those derived from the spectroscopically confirmed Three-year Supernova Legacy Survey (SNLS3). Using only our data, the statistics-only result favors an accelerating universe at 99.96% confidence. Assuming a constant wCDM cosmological model, and combining with H 0 , cosmic microwave background, and luminous red galaxy data, we obtain w = −0.96 +0.10 −0.10 , Ω m = 0.29 +0.02 −0.02 , and Ω k = 0.00 +0.03 −0.02 (statistical errors only), which is competitive with similar spectroscopically confirmed SNe Ia analyses. Overall this comparison is reassuring, considering the lower redshift leverage of the SDSS-II SN sample (z < 0.55) and the lack of spectroscopic confirmation used herein. These results demonstrate the potential of photometrically classified SN Ia samples in improving cosmological constraints.

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SiFTO: An Empirical Method for Fitting SN Ia Light Curves

Cited by 242 publications

References 58 publications

Planck2013 results. XVI. Cosmological parameters

Planck2013 results. XVI. Cosmological parameters

Observational probes of cosmic acceleration

COSMOLOGY WITH PHOTOMETRICALLY CLASSIFIED TYPE Ia SUPERNOVAE FROM THE SDSS-II SUPERNOVA SURVEY

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